diff --git a/src/meta_schedule/mutator/mutate_tile_size.cc b/src/meta_schedule/mutator/mutate_tile_size.cc
index 8fb83147ea7b..ea4e81c16f0c 100644
--- a/src/meta_schedule/mutator/mutate_tile_size.cc
+++ b/src/meta_schedule/mutator/mutate_tile_size.cc
@@ -128,6 +128,13 @@ void FindSampleVectorize(const Trace& trace, std::vector<Instruction>* inst,
     if (inst->kind.same_as(inst_sample_categorical)) {
       ICHECK_EQ(inst->outputs.size(), 1);
       if (annotated.count(inst->outputs[0].get())) {
+        ICHECK_EQ(inst->attrs.size(), 2);
+        std::vector<double> probs =
+            support::AsVector<FloatImm, double>(Downcast<Array<FloatImm>>(inst->attrs[1]));
+        if (probs.size() == 1) {
+          // Skip mutating the sampling instructions who have only single candidate.
+          continue;
+        }
         const auto* d = TVM_TYPE_AS(decision, IntImmNode);
         instructions.push_back(inst);
         decisions.push_back(d->value);
diff --git a/tests/python/unittest/test_meta_schedule_mutator_mutate_tile_size.py b/tests/python/unittest/test_meta_schedule_mutator_mutate_tile_size.py
index 0600c0b79194..c09ef3e87066 100644
--- a/tests/python/unittest/test_meta_schedule_mutator_mutate_tile_size.py
+++ b/tests/python/unittest/test_meta_schedule_mutator_mutate_tile_size.py
@@ -95,5 +95,18 @@ def test_mutate_tile_size_matmul():
     assert len(results) > 15
 
 
+def test_mutate_sample_categorical_single_candidate():
+    mutator = _make_mutator(
+        target=Target("llvm --num-cores=16"),
+    )
+    sch = Schedule(matmul, debug_mask="all")
+    sch.sample_categorical(candidates=[1], probs=[1.0], decision=0)
+
+    # The mutator finds the SampleCategorical has only one candidate, and thus skips it.
+    trace = mutator.apply(sch.trace)
+    assert trace is None
+
+
 if __name__ == "__main__":
     test_mutate_tile_size_matmul()
+    test_mutate_sample_categorical_single_candidate()