diff --git a/rosidl_cli/rosidl_cli/cli.py b/rosidl_cli/rosidl_cli/cli.py
index 18eff8042..9c3f8ac28 100644
--- a/rosidl_cli/rosidl_cli/cli.py
+++ b/rosidl_cli/rosidl_cli/cli.py
@@ -16,6 +16,7 @@
 import signal
 
 from rosidl_cli.command.generate import GenerateCommand
+from rosidl_cli.command.translate import TranslateCommand
 from rosidl_cli.common import get_first_line_doc
 
 
@@ -73,7 +74,7 @@ def main():
         formatter_class=argparse.RawDescriptionHelpFormatter
     )
 
-    commands = [GenerateCommand()]
+    commands = [GenerateCommand(), TranslateCommand()]
 
     # add arguments for command extension(s)
     add_subparsers(
diff --git a/rosidl_cli/rosidl_cli/command/generate/helpers.py b/rosidl_cli/rosidl_cli/command/helpers.py
similarity index 80%
rename from rosidl_cli/rosidl_cli/command/generate/helpers.py
rename to rosidl_cli/rosidl_cli/command/helpers.py
index 643d86813..1dbf1c8eb 100644
--- a/rosidl_cli/rosidl_cli/command/generate/helpers.py
+++ b/rosidl_cli/rosidl_cli/command/helpers.py
@@ -45,33 +45,44 @@ def dependencies_from_include_paths(include_paths):
     })
 
 
-def idl_tuples_from_interface_files(interface_files):
+def interface_path_as_tuple(path):
     """
-    Express ROS interface definition file paths as IDL tuples.
+    Express interface definition file path as an (absolute prefix, relative path) tuple.
 
-    An IDL tuple is a relative path prefixed by by an absolute path against
-    which to resolve it followed by a colon ':'. This function then applies
-    the following logic:
-    - If a given path follows this pattern, it is passed through.
+    An interface definition file path is a relative path, optionally prefixed
+    by a path against which to resolve the former followed by a colon ':'.
+    Thus, this function applies following logic:
+    - If a given path follows this pattern, it is split at the colon ':'
     - If a given path is prefixed by a relative path, it is resolved
       relative to the current working directory.
-    - If a given path has no prefixes, the current working directory is
+    - If a given path has no prefix, the current working directory is
       used as prefix.
     """
+    path_as_string = str(path)
+    if ':' not in path_as_string:
+        prefix = pathlib.Path.cwd()
+    else:
+        prefix, _, path = path_as_string.rpartition(':')
+        prefix = pathlib.Path(os.path.abspath(prefix))
+    path = pathlib.Path(path)
+    if path.is_absolute():
+        raise ValueError('Interface definition file path '
+                         f"'{path}' cannot be absolute")
+    return prefix, path
+
+
+def idl_tuples_from_interface_files(interface_files):
+    """
+    Express ROS interface definition file paths as IDL tuples.
+
+    An IDL tuple is a relative path prefixed by an absolute path against
+    which to resolve it followed by a colon ':'. This function then applies
+    the same logic as `interface_path_as_tuple`.
+    """
     idl_tuples = []
     for path in interface_files:
-        path_as_string = str(path)
-        if ':' not in path_as_string:
-            prefix = pathlib.Path.cwd()
-            stem = path
-        else:
-            prefix, _, stem = path_as_string.rpartition(':')
-            prefix = os.path.abspath(prefix)
-        stem = pathlib.Path(stem)
-        if stem.is_absolute():
-            raise ValueError('Interface definition file path '
-                             f'{stem} cannot be absolute')
-        idl_tuples.append(f'{prefix}:{stem.as_posix()}')
+        prefix, path = interface_path_as_tuple(path)
+        idl_tuples.append(f'{prefix}:{path.as_posix()}')
     return idl_tuples
 
 
diff --git a/rosidl_cli/rosidl_cli/command/translate/__init__.py b/rosidl_cli/rosidl_cli/command/translate/__init__.py
new file mode 100644
index 000000000..20607d25b
--- /dev/null
+++ b/rosidl_cli/rosidl_cli/command/translate/__init__.py
@@ -0,0 +1,98 @@
+# Copyright 2021 Open Source Robotics Foundation, Inc.
+#
+# 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 collections
+import os
+import pathlib
+
+from rosidl_cli.command import Command
+
+from .extensions import load_translate_extensions
+
+
+class TranslateCommand(Command):
+    """Translate interface definition files from one format to another."""
+
+    name = 'translate'
+
+    def add_arguments(self, parser):
+        parser.add_argument(
+            '-o', '--output-path', metavar='PATH',
+            type=pathlib.Path, default=pathlib.Path.cwd(),
+            help=('Path to directory to hold translated interface definition'
+                  "files. Defaults to '.'."))
+        parser.add_argument(
+            '--use', '--translator', metavar='TRANSLATOR_SPEC',
+            dest='translator_specs', action='append', default=[],
+            help=('Translators to be used. If none is given, '
+                  'suitable available ones will be used.')
+        )
+        parser.add_argument(
+            '--to', '--output-format', required=True,
+            metavar='FORMAT', dest='output_format',
+            help='Output format for translate interface definition files.'
+        )
+        parser.add_argument(
+            '--from', '--input-format', default=None,
+            metavar='FORMAT', dest='input_format',
+            help=('Input format for all source interface definition files. '
+                  'If not given, file extensions will be used to deduce '
+                  'the format of each interface definition file.')
+        )
+        parser.add_argument(
+            '-I', '--include-path', metavar='PATH', type=pathlib.Path,
+            dest='include_paths', action='append', default=[],
+            help='Paths to include dependency interface definition files from.'
+        )
+        parser.add_argument(
+            'package_name',
+            help='Name of the package all interface files belong to')
+        parser.add_argument(
+            'interface_files', metavar='interface_file', nargs='+',
+            help=('Normalized relative path to an interface definition file. '
+                  "If prefixed by another path followed by a colon ':', "
+                  'path resolution is performed against such path.')
+        )
+
+    def main(self, *, args):
+        extensions = load_translate_extensions(
+            specs=args.translator_specs,
+            strict=any(args.translator_specs)
+        )
+        if not extensions:
+            return 'No translate extensions found'
+
+        if not args.input_format:
+            interface_files_per_format = collections.defaultdict(list)
+            for interface_file in args.interface_files:
+                input_format = os.path.splitext(interface_file)[-1][1:]
+                interface_files_per_format[input_format].append(interface_file)
+        else:
+            interface_files_per_format = {
+                args.input_format: args.interface_files}
+
+        for input_format, interface_files in interface_files_per_format.items():
+            extension = next((
+                extension for extension in extensions
+                if extension.input_format == input_format and
+                extension.output_format == args.output_format
+            ), None)
+
+            if not extension:
+                return (f"Translation from '{input_format}' to "
+                        f"'{args.output_format}' is not supported")
+
+            extension.translate(
+                args.package_name, interface_files,
+                args.include_paths, args.output_path)
diff --git a/rosidl_cli/rosidl_cli/command/translate/extensions.py b/rosidl_cli/rosidl_cli/command/translate/extensions.py
new file mode 100644
index 000000000..1cb97b5d3
--- /dev/null
+++ b/rosidl_cli/rosidl_cli/command/translate/extensions.py
@@ -0,0 +1,63 @@
+# Copyright 2021 Open Source Robotics Foundation, Inc.
+#
+# 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.
+
+from rosidl_cli.extensions import Extension
+from rosidl_cli.extensions import load_extensions
+
+
+class TranslateCommandExtension(Extension):
+    """
+    The extension point for interface definition translation.
+
+    The following attributes must be defined
+    * `input_format`
+    * `output_format`
+
+    The following methods must be defined:
+    * `translate`
+    """
+
+    def translate(
+        self,
+        package_name,
+        interface_files,
+        include_paths,
+        output_path
+    ):
+        """
+        Translate interface definition files.
+
+        The path to an interface definition file is a relative path optionally
+        prefixed by an absolute path followed by a colon ':', in which case
+        path resolution is to be performed against that absolute path.
+
+        On output, the directory structure specified by this relative path
+        will be replicated e.g. an ``msg/Empty.foo`` file will result in a
+        ``msg/Empty.bar`` file under `output_path`.
+
+        :param package_name: name of the package `interface_file` belongs to
+        :param interface_files: list of paths to interface definition files
+        :param include_paths: list of paths to include dependency interface
+          definition files from
+        :param output_path: path to directory to hold translated interface
+          definition files
+        """
+        raise NotImplementedError()
+
+
+def load_translate_extensions(**kwargs):
+    """Load extensions for interface definition translation."""
+    return load_extensions(
+        'rosidl_cli.command.translate.extensions', **kwargs
+    )
diff --git a/rosidl_cli/test/rosidl_cli/test_generate_helpers.py b/rosidl_cli/test/rosidl_cli/test_helpers.py
similarity index 72%
rename from rosidl_cli/test/rosidl_cli/test_generate_helpers.py
rename to rosidl_cli/test/rosidl_cli/test_helpers.py
index 52c390cc2..5a16f684f 100644
--- a/rosidl_cli/test/rosidl_cli/test_generate_helpers.py
+++ b/rosidl_cli/test/rosidl_cli/test_helpers.py
@@ -18,7 +18,22 @@
 
 import pytest
 
-from rosidl_cli.command.generate.helpers import legacy_generator_arguments_file
+from rosidl_cli.command.helpers import interface_path_as_tuple
+from rosidl_cli.command.helpers import legacy_generator_arguments_file
+
+
+def test_interface_path_as_tuple():
+    prefix, path = interface_path_as_tuple('/tmp:msg/Empty.idl')
+    assert pathlib.Path('msg/Empty.idl') == path
+    assert pathlib.Path(os.path.abspath('/tmp')) == prefix
+
+    prefix, path = interface_path_as_tuple('tmp:msg/Empty.idl')
+    assert pathlib.Path('msg/Empty.idl') == path
+    assert pathlib.Path.cwd() / 'tmp' == prefix
+
+    prefix, path = interface_path_as_tuple('msg/Empty.idl')
+    assert pathlib.Path('msg/Empty.idl') == path
+    assert pathlib.Path.cwd() == prefix
 
 
 @pytest.fixture