diff --git a/cpp/src/arrow/testing/generator.h b/cpp/src/arrow/testing/generator.h
index 6326b416bf925..53a207c473b7a 100644
--- a/cpp/src/arrow/testing/generator.h
+++ b/cpp/src/arrow/testing/generator.h
@@ -306,7 +306,7 @@ ARROW_TESTING_EXPORT std::shared_ptr<ArrayGenerator> Constant(
 /// make a generator that returns an incrementing value
 ///
 /// Note: overflow is not prevented standard unsigned integer overflow applies
-template <typename T = int32_t>
+template <typename T = uint32_t>
 ARROW_TESTING_EXPORT std::shared_ptr<ArrayGenerator> Step(T start = 0, T step = 1) {
   class StepGenerator : public ArrayGenerator {
    public:
diff --git a/cpp/src/arrow/testing/generator_test.cc b/cpp/src/arrow/testing/generator_test.cc
index 3b788ce9e6351..1a2292c2fa640 100644
--- a/cpp/src/arrow/testing/generator_test.cc
+++ b/cpp/src/arrow/testing/generator_test.cc
@@ -40,7 +40,7 @@ TEST(StepTest, Default) {
   for (auto length : {0, 1, 1024}) {
     ARROW_SCOPED_TRACE("length=" + std::to_string(length));
     ASSERT_OK_AND_ASSIGN(auto array, Step()->Generate(length));
-    CheckStep(*array, 0, 1, length);
+    CheckStep(*array, 0u, 1u, length);
   }
 }