diff --git a/cpp/src/arrow/array/array_list_test.cc b/cpp/src/arrow/array/array_list_test.cc
index 4901a1e6fa6..2f5918f79a3 100644
--- a/cpp/src/arrow/array/array_list_test.cc
+++ b/cpp/src/arrow/array/array_list_test.cc
@@ -1600,6 +1600,16 @@ class TestFixedSizeListArray : public ::testing::Test {
   std::shared_ptr<FixedSizeListArray> result_;
 };
 
+// TEST_F(TestFixedSizeListArray, TestUnsafeAppend) {
+//   ASSERT_OK(builder_->Reserve(2));
+//   builder_->UnsafeAppend();
+//   builder_->UnsafeAppend();
+
+//   Done();
+
+//   ASSERT_EQ(result_->length(), 2);
+// }
+
 TEST_F(TestFixedSizeListArray, Equality) {
   Int32Builder* vb = checked_cast<Int32Builder*>(builder_->value_builder());
 
@@ -1722,6 +1732,30 @@ TEST_F(TestFixedSizeListArray, TestBasics) {
   ValidateBasicFixedSizeListArray(result_.get(), values, is_valid);
 }
 
+TEST_F(TestFixedSizeListArray, TestBasicsWithUnsafeAppend) {
+  std::vector<int32_t> values = {0, 1, 2, 3, 4, 5};
+  std::vector<uint8_t> is_valid = {1, 0, 1};
+
+  Int32Builder* vb = checked_cast<Int32Builder*>(builder_->value_builder());
+
+  int pos = 0;
+  ASSERT_OK(builder_->Reserve(values.size() / list_size()));
+  for (size_t i = 0; i < values.size() / list_size(); ++i) {
+    if (is_valid[i] == 0) {
+      ASSERT_OK(builder_->AppendNull());
+      pos += list_size();
+      continue;
+    }
+    builder_->UnsafeAppend();
+    for (int j = 0; j < list_size(); ++j) {
+      ASSERT_OK(vb->Append(values[pos++]));
+    }
+  }
+
+  Done();
+  ValidateBasicFixedSizeListArray(result_.get(), values, is_valid);
+}
+
 TEST_F(TestFixedSizeListArray, BulkAppend) {
   std::vector<int32_t> values = {0, 1, 2, 3, 4, 5};
   std::vector<uint8_t> is_valid = {1, 0, 1};
diff --git a/cpp/src/arrow/array/builder_nested.cc b/cpp/src/arrow/array/builder_nested.cc
index 915fbfbf895..f8475db65b3 100644
--- a/cpp/src/arrow/array/builder_nested.cc
+++ b/cpp/src/arrow/array/builder_nested.cc
@@ -200,7 +200,7 @@ void FixedSizeListBuilder::Reset() {
 
 Status FixedSizeListBuilder::Append() {
   RETURN_NOT_OK(Reserve(1));
-  UnsafeAppendToBitmap(true);
+  UnsafeAppend();
   return Status::OK();
 }
 
diff --git a/cpp/src/arrow/array/builder_nested.h b/cpp/src/arrow/array/builder_nested.h
index fdbeb0cd7d1..9abfdb6202a 100644
--- a/cpp/src/arrow/array/builder_nested.h
+++ b/cpp/src/arrow/array/builder_nested.h
@@ -725,6 +725,13 @@ class ARROW_EXPORT FixedSizeListBuilder : public ArrayBuilder {
     return std::numeric_limits<FixedSizeListType::offset_type>::max() - 1;
   }
 
+  /// \brief UnsafeAppend a valid fixed length list.
+  ///
+  /// This function affects only the validity bitmap; the child values must be appended
+  /// using the child array builder. The caller must ensure that sufficient capacity is
+  /// available.
+  void UnsafeAppend() { UnsafeAppendToBitmap(true); }
+
  protected:
   std::shared_ptr<Field> value_field_;
   const int32_t list_size_;