diff --git a/spec/compiler/parser/parser_spec.cr b/spec/compiler/parser/parser_spec.cr
index abe382f0d5fc..8e4e0777b813 100644
--- a/spec/compiler/parser/parser_spec.cr
+++ b/spec/compiler/parser/parser_spec.cr
@@ -4,8 +4,8 @@ private def regex(string, options = Regex::Options::None)
   RegexLiteral.new(StringLiteral.new(string), options)
 end
 
-private def it_parses(string, expected_node, file = __FILE__, line = __LINE__)
-  it "parses #{string.dump}", file, line do
+private def it_parses(string, expected_node, file = __FILE__, line = __LINE__, *, focus : Bool = false)
+  it "parses #{string.dump}", file, line, focus: focus do
     parser = Parser.new(string)
     parser.filename = "/foo/bar/baz.cr"
     node = parser.parse
@@ -316,6 +316,26 @@ module Crystal
     it_parses "def foo(@@var = 1); 1; end", Def.new("foo", [Arg.new("var", 1.int32)], [Assign.new("@@var".class_var, "var".var), 1.int32] of ASTNode)
     it_parses "def foo(&@block); end", Def.new("foo", body: Assign.new("@block".instance_var, "block".var), block_arg: Arg.new("block"), yields: 0)
 
+    # Defs with annotated parameters
+    it_parses "def foo(@[Foo] var); end", Def.new("foo", ["var".arg(annotations: ["Foo".ann])])
+    it_parses "def foo(@[Foo] outer inner); end", Def.new("foo", ["inner".arg(annotations: ["Foo".ann], external_name: "outer")])
+    it_parses "def foo(@[Foo]  var); end", Def.new("foo", ["var".arg(annotations: ["Foo".ann])])
+    it_parses "def foo(a, @[Foo] var); end", Def.new("foo", ["a".arg, "var".arg(annotations: ["Foo".ann])])
+    it_parses "def foo(a, @[Foo] &block); end", Def.new("foo", ["a".arg], block_arg: "block".arg(annotations: ["Foo".ann]), yields: 0)
+    it_parses "def foo(@[Foo] @var); end", Def.new("foo", ["var".arg(annotations: ["Foo".ann])], [Assign.new("@var".instance_var, "var".var)] of ASTNode)
+    it_parses "def foo(@[Foo] var : Int32); end", Def.new("foo", ["var".arg(restriction: "Int32".path, annotations: ["Foo".ann])])
+    it_parses "def foo(@[Foo] @[Bar] var : Int32); end", Def.new("foo", ["var".arg(restriction: "Int32".path, annotations: ["Foo".ann, "Bar".ann])])
+    it_parses "def foo(@[Foo] &@block); end", Def.new("foo", body: Assign.new("@block".instance_var, "block".var), block_arg: "block".arg(annotations: ["Foo".ann]), yields: 0)
+    it_parses "def foo(@[Foo] *args); end", Def.new("foo", args: ["args".arg(annotations: ["Foo".ann])], splat_index: 0)
+    it_parses "def foo(@[Foo] **args); end", Def.new("foo", double_splat: "args".arg(annotations: ["Foo".ann]))
+    it_parses <<-CR, Def.new("foo", ["id".arg(restriction: "Int32".path, annotations: ["Foo".ann]), "name".arg(restriction: "String".path, annotations: ["Bar".ann])])
+      def foo(
+        @[Foo]
+        id : Int32,
+        @[Bar] name : String
+      ); end
+    CR
+
     it_parses "def foo(\n&block\n); end", Def.new("foo", block_arg: Arg.new("block"), yields: 0)
     it_parses "def foo(&block :\n Int ->); end", Def.new("foo", block_arg: Arg.new("block", restriction: ProcNotation.new(["Int".path] of ASTNode)), yields: 1)
     it_parses "def foo(&block : Int ->\n); end", Def.new("foo", block_arg: Arg.new("block", restriction: ProcNotation.new(["Int".path] of ASTNode)), yields: 1)
@@ -983,6 +1003,22 @@ module Crystal
     it_parses "macro foo;bar(end: 1);end", Macro.new("foo", body: Expressions.from(["bar(".macro_literal, "end: 1);".macro_literal] of ASTNode))
     it_parses "def foo;bar(end: 1);end", Def.new("foo", body: Expressions.from([Call.new(nil, "bar", named_args: [NamedArgument.new("end", 1.int32)])] of ASTNode))
 
+    # Macros with annotated parameters
+    it_parses "macro foo(@[Foo] var);end", Macro.new("foo", ["var".arg(annotations: ["Foo".ann])], Expressions.new)
+    it_parses "macro foo(@[Foo] outer inner);end", Macro.new("foo", ["inner".arg(annotations: ["Foo".ann], external_name: "outer")], Expressions.new)
+    it_parses "macro foo(@[Foo]  var);end", Macro.new("foo", ["var".arg(annotations: ["Foo".ann])], Expressions.new)
+    it_parses "macro foo(a, @[Foo] var);end", Macro.new("foo", ["a".arg, "var".arg(annotations: ["Foo".ann])], Expressions.new)
+    it_parses "macro foo(a, @[Foo] &block);end", Macro.new("foo", ["a".arg], Expressions.new, block_arg: "block".arg(annotations: ["Foo".ann]))
+    it_parses "macro foo(@[Foo] *args);end", Macro.new("foo", ["args".arg(annotations: ["Foo".ann])], Expressions.new, splat_index: 0)
+    it_parses "macro foo(@[Foo] **args);end", Macro.new("foo", body: Expressions.new, double_splat: "args".arg(annotations: ["Foo".ann]))
+    it_parses <<-CR, Macro.new("foo", ["id".arg(annotations: ["Foo".ann]), "name".arg(annotations: ["Bar".ann])], Expressions.new)
+      macro foo(
+        @[Foo]
+        id,
+        @[Bar] name
+      );end
+    CR
+
     assert_syntax_error "macro foo; {% foo = 1 }; end"
     assert_syntax_error "macro def foo : String; 1; end"
 
diff --git a/spec/compiler/parser/to_s_spec.cr b/spec/compiler/parser/to_s_spec.cr
index a5072cdcebca..4e72464f22c2 100644
--- a/spec/compiler/parser/to_s_spec.cr
+++ b/spec/compiler/parser/to_s_spec.cr
@@ -70,7 +70,9 @@ describe "ASTNode#to_s" do
   expect_to_s %[1 & 2 & (3 | 4)], %[(1 & 2) & (3 | 4)]
   expect_to_s %[(1 & 2) & (3 | 4)]
   expect_to_s "def foo(x : T = 1)\nend"
+  expect_to_s "def foo(@[Foo] x : T = 1)\nend"
   expect_to_s "def foo(x : X, y : Y) forall X, Y\nend"
+  expect_to_s "def foo(x : X, @[Foo] y : Y) forall X, Y\nend"
   expect_to_s %(foo : A | (B -> C))
   expect_to_s %(foo : (A | B).class)
   expect_to_s %[%("\#{foo}")], %["\\"\#{foo}\\""]
@@ -82,22 +84,39 @@ describe "ASTNode#to_s" do
   expect_to_s "_foo.bar"
   expect_to_s "1.responds_to?(:to_s)"
   expect_to_s "1.responds_to?(:\"&&\")"
+  expect_to_s "macro foo(&block)\nend"
+  expect_to_s "macro foo(&)\nend"
+  expect_to_s "macro foo(*, __var var)\nend"
+  expect_to_s "macro foo(*, var)\nend"
+  expect_to_s "macro foo(*var)\nend"
+  expect_to_s "macro foo(@[Foo] &)\nend"
+  expect_to_s "macro foo(@[Foo] &block)\nend"
   expect_to_s "macro foo(x, *y)\nend"
+  expect_to_s "macro foo(x, @[Foo] *y)\nend"
+  expect_to_s "macro foo(@[Foo] x, @[Foo] *y)\nend"
   expect_to_s "{ {1, 2, 3} }"
   expect_to_s "{ {1 => 2} }"
   expect_to_s "{ {1, 2, 3} => 4 }"
   expect_to_s "{ {foo: 2} }"
   expect_to_s "def foo(*args)\nend"
+  expect_to_s "def foo(@[Foo] *args)\nend"
   expect_to_s "def foo(*args : _)\nend"
   expect_to_s "def foo(**args)\nend"
+  expect_to_s "def foo(@[Foo] **args)\nend"
   expect_to_s "def foo(**args : T)\nend"
   expect_to_s "def foo(x, **args)\nend"
+  expect_to_s "def foo(x, @[Foo] **args)\nend"
   expect_to_s "def foo(x, **args, &block)\nend"
+  expect_to_s "def foo(@[Foo] x, @[Bar] **args, @[Baz] &block)\nend"
   expect_to_s "def foo(x, **args, &block : (_ -> _))\nend"
   expect_to_s "def foo(& : (->))\nend"
+  expect_to_s "macro foo(@[Foo] id)\nend"
   expect_to_s "macro foo(**args)\nend"
+  expect_to_s "macro foo(@[Foo] **args)\nend"
   expect_to_s "macro foo(x, **args)\nend"
+  expect_to_s "macro foo(x, @[Foo] **args)\nend"
   expect_to_s "def foo(x y)\nend"
+  expect_to_s "def foo(@[Foo] x y)\nend"
   expect_to_s %(foo("bar baz": 2))
   expect_to_s %(Foo("bar baz": Int32))
   expect_to_s %(Foo())
diff --git a/spec/compiler/semantic/annotation_spec.cr b/spec/compiler/semantic/annotation_spec.cr
index 2e6670b62f09..89dd5e734243 100644
--- a/spec/compiler/semantic/annotation_spec.cr
+++ b/spec/compiler/semantic/annotation_spec.cr
@@ -916,6 +916,78 @@ describe "Semantic: annotation" do
         {{ Child.superclass.annotation(Ann)[0] }}
       )) { int32 }
     end
+
+    it "finds annotation on method arg" do
+      assert_type(%(
+        annotation Ann; end
+
+        def foo(
+          @[Ann] foo : Int32
+        )
+        end
+
+        {% if @top_level.methods.find(&.name.==("foo")).args.first.annotation(Ann) %}
+          1
+        {% else %}
+          'a'
+        {% end %}
+      )) { int32 }
+    end
+
+    it "finds annotation on method splat arg" do
+      assert_type(%(
+        annotation Ann; end
+
+        def foo(
+          id : Int32,
+          @[Ann] *nums : Int32
+        )
+        end
+
+        {% if @top_level.methods.find(&.name.==("foo")).args[1].annotation(Ann) %}
+          1
+        {% else %}
+          'a'
+        {% end %}
+      )) { int32 }
+    end
+
+    it "finds annotation on method double splat arg" do
+      assert_type(%(
+        annotation Ann; end
+
+        def foo(
+          id : Int32,
+          @[Ann] **nums
+        )
+        end
+
+        {% if @top_level.methods.find(&.name.==("foo")).double_splat.annotation(Ann) %}
+          1
+        {% else %}
+          'a'
+        {% end %}
+      )) { int32 }
+    end
+
+    it "finds annotation on an restricted method block arg" do
+      assert_type(%(
+        annotation Ann; end
+
+        def foo(
+          id : Int32,
+          @[Ann] &block : Int32 ->
+        )
+          yield 10
+        end
+
+        {% if @top_level.methods.find(&.name.==("foo")).block_arg.annotation(Ann) %}
+          1
+        {% else %}
+          'a'
+        {% end %}
+      )) { int32 }
+    end
   end
 
   it "errors when annotate instance variable in subclass" do
diff --git a/spec/support/syntax.cr b/spec/support/syntax.cr
index 67634180f565..5514fc1d4acf 100644
--- a/spec/support/syntax.cr
+++ b/spec/support/syntax.cr
@@ -54,8 +54,12 @@ class String
     Var.new self
   end
 
-  def arg(default_value = nil, restriction = nil, external_name = nil)
-    Arg.new self, default_value: default_value, restriction: restriction, external_name: external_name
+  def ann
+    Annotation.new path
+  end
+
+  def arg(default_value = nil, restriction = nil, external_name = nil, annotations = nil)
+    Arg.new self, default_value: default_value, restriction: restriction, external_name: external_name, parsed_annotations: annotations
   end
 
   def call
diff --git a/src/compiler/crystal/macros.cr b/src/compiler/crystal/macros.cr
index c1123ddbc787..d4ce2d4b995c 100644
--- a/src/compiler/crystal/macros.cr
+++ b/src/compiler/crystal/macros.cr
@@ -1114,6 +1114,16 @@ module Crystal::Macros
 
   # A def argument.
   class Arg < ASTNode
+    # Returns the last `Annotation` with the given `type`
+    # attached to this arg or `NilLiteral` if there are none.
+    def annotation(type : TypeNode) : Annotation | NilLiteral
+    end
+
+    # Returns an array of annotations with the given `type`
+    # attached to this arg, or an empty `ArrayLiteral` if there are none.
+    def annotations(type : TypeNode) : ArrayLiteral(Annotation)
+    end
+
     # Returns the external name of this argument.
     #
     # For example, for `def write(to file)` returns `to`.
diff --git a/src/compiler/crystal/macros/methods.cr b/src/compiler/crystal/macros/methods.cr
index 6ff11ad10ee5..4058f8590080 100644
--- a/src/compiler/crystal/macros/methods.cr
+++ b/src/compiler/crystal/macros/methods.cr
@@ -1342,6 +1342,16 @@ module Crystal
         interpret_check_args { default_value || Nop.new }
       when "restriction"
         interpret_check_args { restriction || Nop.new }
+      when "annotation"
+        fetch_annotation(self, method, args, named_args, block) do |type|
+          self.annotation(type)
+        end
+      when "annotations"
+        fetch_annotation(self, method, args, named_args, block) do |type|
+          annotations = self.annotations(type)
+          return ArrayLiteral.new if annotations.nil?
+          ArrayLiteral.map(annotations, &.itself)
+        end
       else
         super
       end
diff --git a/src/compiler/crystal/semantic/ast.cr b/src/compiler/crystal/semantic/ast.cr
index fd13848b1978..3eee08ca3537 100644
--- a/src/compiler/crystal/semantic/ast.cr
+++ b/src/compiler/crystal/semantic/ast.cr
@@ -121,6 +121,8 @@ module Crystal
   end
 
   class Arg
+    include Annotatable
+
     def initialize(@name : String, @default_value : ASTNode? = nil, @restriction : ASTNode? = nil, external_name : String? = nil, @type : Type? = nil)
       @external_name = external_name || @name
     end
diff --git a/src/compiler/crystal/semantic/to_s.cr b/src/compiler/crystal/semantic/to_s.cr
index 38932f11aa05..8c91426bc379 100644
--- a/src/compiler/crystal/semantic/to_s.cr
+++ b/src/compiler/crystal/semantic/to_s.cr
@@ -3,6 +3,19 @@ require "../syntax/to_s"
 module Crystal
   class ToSVisitor
     def visit(node : Arg)
+      if parsed_annotations = node.parsed_annotations
+        parsed_annotations.each do |ann|
+          ann.accept self
+          @str << ' '
+        end
+      end
+
+      case @current_arg_type
+      when .splat?        then @str << '*'
+      when .double_splat? then @str << "**"
+      when .block_arg?    then @str << '&'
+      end
+
       if node.external_name != node.name
         visit_named_arg_name(node.external_name)
         @str << ' '
@@ -24,6 +37,8 @@ module Crystal
         default_value.accept self
       end
       false
+    ensure
+      @current_arg_type = :none
     end
 
     def visit(node : Primitive)
diff --git a/src/compiler/crystal/semantic/top_level_visitor.cr b/src/compiler/crystal/semantic/top_level_visitor.cr
index 9a16767b8757..dd062f77a515 100644
--- a/src/compiler/crystal/semantic/top_level_visitor.cr
+++ b/src/compiler/crystal/semantic/top_level_visitor.cr
@@ -327,6 +327,10 @@ class Crystal::TopLevelVisitor < Crystal::SemanticVisitor
     node.doc ||= annotations_doc(annotations)
     check_ditto node, node.location
 
+    node.args.each &.accept self
+    node.double_splat.try &.accept self
+    node.block_arg.try &.accept self
+
     node.set_type @program.nil
 
     if node.name == "finished"
@@ -347,6 +351,16 @@ class Crystal::TopLevelVisitor < Crystal::SemanticVisitor
     false
   end
 
+  def visit(node : Arg)
+    if anns = node.parsed_annotations
+      process_annotations anns do |annotation_type, ann|
+        node.add_annotation annotation_type, ann
+      end
+    end
+
+    false
+  end
+
   def visit(node : Def)
     check_outside_exp node, "declare def"
 
@@ -363,6 +377,10 @@ class Crystal::TopLevelVisitor < Crystal::SemanticVisitor
     node.doc ||= annotations_doc(annotations)
     check_ditto node, node.location
 
+    node.args.each &.accept self
+    node.double_splat.try &.accept self
+    node.block_arg.try &.accept self
+
     is_instance_method = false
 
     target_type = case receiver = node.receiver
diff --git a/src/compiler/crystal/syntax/ast.cr b/src/compiler/crystal/syntax/ast.cr
index 50b6f5da6503..1d8da8f60652 100644
--- a/src/compiler/crystal/syntax/ast.cr
+++ b/src/compiler/crystal/syntax/ast.cr
@@ -989,8 +989,9 @@ module Crystal
     property default_value : ASTNode?
     property restriction : ASTNode?
     property doc : String?
+    property parsed_annotations : Array(Annotation)?
 
-    def initialize(@name : String, @default_value : ASTNode? = nil, @restriction : ASTNode? = nil, external_name : String? = nil)
+    def initialize(@name : String, @default_value : ASTNode? = nil, @restriction : ASTNode? = nil, external_name : String? = nil, @parsed_annotations : Array(Annotation)? = nil)
       @external_name = external_name || @name
     end
 
@@ -1004,10 +1005,10 @@ module Crystal
     end
 
     def clone_without_location
-      Arg.new @name, @default_value.clone, @restriction.clone, @external_name.clone
+      Arg.new @name, @default_value.clone, @restriction.clone, @external_name.clone, @parsed_annotations.clone
     end
 
-    def_equals_and_hash name, default_value, restriction, external_name
+    def_equals_and_hash name, default_value, restriction, external_name, parsed_annotations
   end
 
   # The Proc notation in the type grammar:
diff --git a/src/compiler/crystal/syntax/parser.cr b/src/compiler/crystal/syntax/parser.cr
index 5be39462c8c8..08a04342a27d 100644
--- a/src/compiler/crystal/syntax/parser.cr
+++ b/src/compiler/crystal/syntax/parser.cr
@@ -3721,9 +3721,18 @@ module Crystal
       double_splat : Bool
 
     def parse_arg(args, extra_assigns, parentheses, found_default_value, found_splat, found_double_splat, allow_restrictions)
+      annotations = nil
+
+      # Parse annotations first since they would be before any actual arg tokens.
+      # Do this in a loop to account for multiple annotations.
+      while @token.type.op_at_lsquare?
+        (annotations ||= Array(Annotation).new) << parse_annotation
+        skip_space_or_newline
+      end
+
       if @token.type.op_amp?
         next_token_skip_space_or_newline
-        block_arg = parse_block_arg(extra_assigns)
+        block_arg = parse_block_arg(extra_assigns, annotations)
         skip_space_or_newline
         # When block_arg.name is empty, this is an anonymous parameter.
         # An anonymous parameter should not conflict other parameters names.
@@ -3854,14 +3863,14 @@ module Crystal
 
       raise "BUG: arg_name is nil" unless arg_name
 
-      arg = Arg.new(arg_name, default_value, restriction, external_name: external_name).at(arg_location)
+      arg = Arg.new(arg_name, default_value, restriction, external_name: external_name, parsed_annotations: annotations).at(arg_location)
       args << arg
       push_var arg
 
       ArgExtras.new(nil, !!default_value, splat, !!double_splat)
     end
 
-    def parse_block_arg(extra_assigns)
+    def parse_block_arg(extra_assigns, annotations)
       name_location = @token.location
 
       if @token.type.op_rparen? || @token.type.newline? || @token.type.op_colon?
@@ -3882,7 +3891,7 @@ module Crystal
         type_spec = parse_bare_proc_type
       end
 
-      block_arg = Arg.new(arg_name, restriction: type_spec).at(name_location)
+      block_arg = Arg.new(arg_name, restriction: type_spec, parsed_annotations: annotations).at(name_location)
 
       push_var block_arg
 
diff --git a/src/compiler/crystal/syntax/to_s.cr b/src/compiler/crystal/syntax/to_s.cr
index a4ab440fc8b5..a9a12a35c3ae 100644
--- a/src/compiler/crystal/syntax/to_s.cr
+++ b/src/compiler/crystal/syntax/to_s.cr
@@ -16,6 +16,14 @@ module Crystal
   class ToSVisitor < Visitor
     @str : IO
     @macro_expansion_pragmas : Hash(Int32, Array(Lexer::LocPragma))?
+    @current_arg_type : DefArgType = :none
+
+    private enum DefArgType
+      NONE
+      SPLAT
+      DOUBLE_SPLAT
+      BLOCK_ARG
+    end
 
     def initialize(@str = IO::Memory.new, @macro_expansion_pragmas = nil, @emit_doc = false)
       @indent = 0
@@ -613,19 +621,19 @@ module Crystal
         printed_arg = false
         node.args.each_with_index do |arg, i|
           @str << ", " if printed_arg
-          @str << '*' if node.splat_index == i
+          @current_arg_type = :splat if node.splat_index == i
           arg.accept self
           printed_arg = true
         end
         if double_splat = node.double_splat
+          @current_arg_type = :double_splat
           @str << ", " if printed_arg
-          @str << "**"
           double_splat.accept self
           printed_arg = true
         end
         if block_arg = node.block_arg
+          @current_arg_type = :block_arg
           @str << ", " if printed_arg
-          @str << '&'
           block_arg.accept self
           printed_arg = true
         end
@@ -659,19 +667,19 @@ module Crystal
         printed_arg = false
         node.args.each_with_index do |arg, i|
           @str << ", " if printed_arg
-          @str << '*' if i == node.splat_index
+          @current_arg_type = :splat if i == node.splat_index
           arg.accept self
           printed_arg = true
         end
         if double_splat = node.double_splat
           @str << ", " if printed_arg
-          @str << "**"
+          @current_arg_type = :double_splat
           double_splat.accept self
           printed_arg = true
         end
         if block_arg = node.block_arg
           @str << ", " if printed_arg
-          @str << '&'
+          @current_arg_type = :block_arg
           block_arg.accept self
         end
         @str << ')'
@@ -771,6 +779,19 @@ module Crystal
     end
 
     def visit(node : Arg)
+      if parsed_annotations = node.parsed_annotations
+        parsed_annotations.each do |ann|
+          ann.accept self
+          @str << ' '
+        end
+      end
+
+      case @current_arg_type
+      when .splat?        then @str << '*'
+      when .double_splat? then @str << "**"
+      when .block_arg?    then @str << '&'
+      end
+
       if node.external_name != node.name
         visit_named_arg_name(node.external_name)
         @str << ' '
@@ -789,6 +810,8 @@ module Crystal
         default_value.accept self
       end
       false
+    ensure
+      @current_arg_type = :none
     end
 
     def visit(node : ProcNotation)