diff --git a/rosidl_generator_py/CMakeLists.txt b/rosidl_generator_py/CMakeLists.txt
index acffa894..c6cc067e 100644
--- a/rosidl_generator_py/CMakeLists.txt
+++ b/rosidl_generator_py/CMakeLists.txt
@@ -56,6 +56,7 @@ if(BUILD_TESTING)
       ${test_interface_files_MSG_FILES}
       # Cases not covered by test_interface_files
       msg/BuiltinTypeSequencesIdl.idl
+      msg/ByteArray.msg
       msg/StringArrays.msg
       msg/Property.msg
       ADD_LINTER_TESTS
@@ -88,6 +89,13 @@ if(BUILD_TESTING)
       APPEND_LIBRARY_DIRS "${_append_library_dirs}"
       WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/rosidl_generator_py"
     )
+
+    ament_add_pytest_test(test_byte_array_py test/test_byte_array.py
+      PYTHON_EXECUTABLE "${BUILDTYPE_PYTHON_EXECUTABLE}"
+      APPEND_ENV "PYTHONPATH=${pythonpath}"
+      APPEND_LIBRARY_DIRS "${_append_library_dirs}"
+      WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/rosidl_generator_py"
+    )
   endif()
 endif()
 
diff --git a/rosidl_generator_py/msg/ByteArray.msg b/rosidl_generator_py/msg/ByteArray.msg
new file mode 100644
index 00000000..fb7239a1
--- /dev/null
+++ b/rosidl_generator_py/msg/ByteArray.msg
@@ -0,0 +1 @@
+byte[] data
diff --git a/rosidl_generator_py/resource/_msg.py.em b/rosidl_generator_py/resource/_msg.py.em
index 8c21e552..745bf14c 100644
--- a/rosidl_generator_py/resource/_msg.py.em
+++ b/rosidl_generator_py/resource/_msg.py.em
@@ -427,6 +427,7 @@ if isinstance(type_, AbstractNestedType):
 import inspect
 import builtins
 noqa_string = ''
+byte_array_detected = False
 if member.name in dict(inspect.getmembers(builtins)).keys():
     noqa_string = '  # noqa: A003'
 }@
@@ -503,8 +504,16 @@ if member.name in dict(inspect.getmembers(builtins)).keys():
 @{assert_msg_suffixes.insert(1, 'with length %d' % member.type.size)}@
 @[      end if]@
 @[    end if]@
-                 all(isinstance(v, @(get_python_type(type_))) for v in value) and
 @{assert_msg_suffixes.append("and each value of type '%s'" % get_python_type(type_))}@
+@[    if get_python_type(type_) == 'bytes']@
+@{byte_array_detected = True}@
+@{assert_msg_suffixes.append("or type 'int' in range(0, 255)")}@
+                 (isinstance(value, @(get_python_type(type_))) or
+                  all(isinstance(v, @(get_python_type(type_))) for v in value) or
+                  all(isinstance(v, int) for v in value)) and
+@[    else]@
+                 all(isinstance(v, @(get_python_type(type_))) for v in value) and
+@[    end if]@
 @[    if isinstance(type_, BasicType) and type_.typename in SIGNED_INTEGER_TYPES]@
 @{
 nbits = int(type_.typename[3:])
@@ -604,6 +613,13 @@ bound = 1.7976931348623157e+308
         self._@(member.name) = array.array('@(SPECIAL_NESTED_BASIC_TYPES[member.type.value_type.typename]['type_code'])', value)
 @[    end if]@
 @[  else]@
+@[    if byte_array_detected]@
+        if any(isinstance(v, int) for v in value):
+            self._@(member.name) = bytes(value)
+        else:
+            self._@(member.name) = value
+@[    else]@
         self._@(member.name) = value
+@[    end if]@
 @[  end if]@
 @[end for]@
diff --git a/rosidl_generator_py/test/test_byte_array.py b/rosidl_generator_py/test/test_byte_array.py
new file mode 100644
index 00000000..fffedffa
--- /dev/null
+++ b/rosidl_generator_py/test/test_byte_array.py
@@ -0,0 +1,75 @@
+# Copyright 2022 Sony Group Corporation.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pytest
+from rosidl_generator_py.msg import ByteArray
+
+
+def test_msg_bytearray():
+    msg = ByteArray()
+
+    # types
+    assert isinstance(msg.data, list)
+
+    # default values
+    assert [] == msg.data
+
+    # set values
+    l1 = [1, 2, 3]
+    msg.data = l1
+    # get values
+    assert bytes(l1) == msg.data
+
+    # set values
+    l2 = {1, 2, 3}
+    msg.data = l2
+    # get values
+    assert bytes(l2) == msg.data
+
+    from collections import UserList
+    # set values
+    l3 = UserList(l1)
+    msg.data = l3
+    # get values
+    assert bytes(l3) == msg.data
+
+    # set values
+    l4 = bytes('123', 'utf-8')
+    msg.data = l4
+    # get values
+    assert l4 == msg.data
+
+    # set values
+    l5 = [b'1', b'2', b'3']
+    msg.data = l5
+    # get values
+    assert l5 == msg.data
+
+    # set values
+    l6 = ['a', 'b']
+    msg.data = l6
+    # get values
+    assert l6 == msg.data
+
+
+def test_msg_bytearray_exception():
+    msg = ByteArray()
+
+    with pytest.raises(ValueError):
+        l1 = [1, 2, 256]
+        msg.data = l1
+
+    with pytest.raises(TypeError):
+        l2 = [1, b'2', b'3']
+        msg.data = l2