diff --git a/extensions/grpc/deployment/src/test/proto/goodbyeworld.proto b/extensions/grpc/deployment/src/test/proto/goodbyeworld.proto
index f86e335ebe66df..ffdc1defd18f0a 100644
--- a/extensions/grpc/deployment/src/test/proto/goodbyeworld.proto
+++ b/extensions/grpc/deployment/src/test/proto/goodbyeworld.proto
@@ -10,7 +10,7 @@ package goodbyeworld;
 // The farewell service definition.
 service Farewell {
     // Sends a farewell
-    rpc SayGoodbye (GoodbyeRequest) returns (GoodbyeReply) {}
+    rpc Say_goodbye (GoodbyeRequest) returns (GoodbyeReply) {}
 }
 
 // The request message containing the user's name.
@@ -21,4 +21,4 @@ message GoodbyeRequest {
 // The response message containing the farewells
 message GoodbyeReply {
     string message = 1;
-}
\ No newline at end of file
+}
diff --git a/extensions/grpc/protoc/pom.xml b/extensions/grpc/protoc/pom.xml
index 4c5c1266a7f6eb..15b8037182f6b3 100644
--- a/extensions/grpc/protoc/pom.xml
+++ b/extensions/grpc/protoc/pom.xml
@@ -27,6 +27,11 @@
                 </exclusion>
             </exclusions>
         </dependency>
+        <dependency>
+           <groupId>org.junit.jupiter</groupId>
+           <artifactId>junit-jupiter</artifactId>
+           <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
diff --git a/extensions/grpc/protoc/src/main/java/io/quarkus/grpc/protoc/plugin/MutinyGrpcGenerator.java b/extensions/grpc/protoc/src/main/java/io/quarkus/grpc/protoc/plugin/MutinyGrpcGenerator.java
index 348b88c57c01d5..99d91812542b19 100644
--- a/extensions/grpc/protoc/src/main/java/io/quarkus/grpc/protoc/plugin/MutinyGrpcGenerator.java
+++ b/extensions/grpc/protoc/src/main/java/io/quarkus/grpc/protoc/plugin/MutinyGrpcGenerator.java
@@ -1,5 +1,6 @@
 package io.quarkus.grpc.protoc.plugin;
 
+import java.beans.Introspector;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -8,6 +9,8 @@
 import java.util.logging.Logger;
 import java.util.stream.Collectors;
 
+import javax.lang.model.SourceVersion;
+
 import com.google.common.base.Strings;
 import com.google.common.html.HtmlEscapers;
 import com.google.protobuf.DescriptorProtos;
@@ -137,7 +140,7 @@ private ServiceContext buildServiceContext(DescriptorProtos.ServiceDescriptorPro
     private MethodContext buildMethodContext(DescriptorProtos.MethodDescriptorProto methodProto, ProtoTypeMap typeMap,
             List<DescriptorProtos.SourceCodeInfo.Location> locations, int methodNumber) {
         MethodContext methodContext = new MethodContext();
-        methodContext.methodName = lowerCaseFirst(methodProto.getName());
+        methodContext.methodName = adaptMethodName(methodProto.getName());
         methodContext.inputType = typeMap.toJavaTypeName(methodProto.getInputType());
         methodContext.outputType = typeMap.toJavaTypeName(methodProto.getOutputType());
         methodContext.deprecated = methodProto.getOptions() != null && methodProto.getOptions().getDeprecated();
@@ -171,8 +174,31 @@ private MethodContext buildMethodContext(DescriptorProtos.MethodDescriptorProto
         return methodContext;
     }
 
-    private String lowerCaseFirst(String s) {
-        return Character.toLowerCase(s.charAt(0)) + s.substring(1);
+    static String adaptMethodName(String name) {
+        // We need to adjust the method name in the same way as the grpc-java compiler does:
+        // 1. Decapitalize
+        // 2. Replace an underscore and capitalize the following letter
+        // 3. Append the underscore for a java keyword
+        // (these rules are bit odd but we need to follow them unless we get rid of the grpc-java compiler)
+        // https://github.com/quarkusio/quarkus/issues/27170
+        name = Introspector.decapitalize(name);
+        if (name.contains("_")) {
+            StringBuilder res = new StringBuilder();
+            for (String str : name.split("_")) {
+                if (res.length() == 0) {
+                    res.append(str);
+                } else {
+                    res.append(Character.toUpperCase(str.charAt(0)));
+                    if (str.length() > 1) {
+                        res.append(str.substring(1));
+                    }
+                }
+            }
+            name = res.toString();
+        } else if (SourceVersion.isKeyword(name)) {
+            name += "_";
+        }
+        return name;
     }
 
     private List<PluginProtos.CodeGeneratorResponse.File> generateFiles(List<ServiceContext> services) {
diff --git a/extensions/grpc/protoc/src/test/java/io/quarkus/grpc/protoc/plugin/MutinyGrpcGeneratorTest.java b/extensions/grpc/protoc/src/test/java/io/quarkus/grpc/protoc/plugin/MutinyGrpcGeneratorTest.java
new file mode 100644
index 00000000000000..d6efce57dd03b5
--- /dev/null
+++ b/extensions/grpc/protoc/src/test/java/io/quarkus/grpc/protoc/plugin/MutinyGrpcGeneratorTest.java
@@ -0,0 +1,18 @@
+package io.quarkus.grpc.protoc.plugin;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class MutinyGrpcGeneratorTest {
+
+    @Test
+    public void testAdaptMethodName() {
+        assertEquals("sayHello", MutinyGrpcGenerator.adaptMethodName("SayHello"));
+        assertEquals("sayHello", MutinyGrpcGenerator.adaptMethodName("Say_Hello"));
+        assertEquals("sayHello", MutinyGrpcGenerator.adaptMethodName("Say_hello"));
+        assertEquals("sayHelloAndBye", MutinyGrpcGenerator.adaptMethodName("Say_Hello_and_Bye"));
+        assertEquals("return", MutinyGrpcGenerator.adaptMethodName("return_"));
+    }
+
+}