diff --git a/README.md b/README.md
index 635f821..9396bc1 100644
--- a/README.md
+++ b/README.md
@@ -18,20 +18,39 @@ pip install -e .
 
 Then you can use changelog from anywhere:
 ````
-usage: changelog.py [-h] [--log-level LOG_LEVEL] repo-url
+usage: changelog.py [-h] [--log-level LOG_LEVEL] [--update] [--name NAME] repo-url
 
 Changelog generator script
 
 required arguments:
-  repo-url               Repository url in the format <GITHUB_USER/REPO_NAME>. Example: neuropoly/spinalcordtoolbox
+  repo-url              Repository url in the format <GITHUB_USER/REPO_NAME>. Example: neuropoly/spinalcordtoolbox
 
 optional arguments:
-  -h, --help             show this help message and exit
-  --log-level LOG_LEVEL  Logging level (eg. INFO, see Python logging docs)
+  -h, --help            show this help message and exit
+  --log-level LOG_LEVEL Logging level (eg. INFO, see Python logging docs)
+  --update              Update an existing changelog file by prepending current changelog to it.
+  --name NAME           Existing changelog file to use (by default use CHANGES.md).
+
+
 ````
 
+### Examples
+```
+# create a new changelog file [user]_[repo]_changelog.[tagId].md for spinalcordtoolbox
+changelog neuropoly/spinalcordtoolbox
+
+# prepend to an existing CHANGES.md file (default)
+changelog neuropoly/spinalcordtoolbox --update
+
+# prepend to an existing CUSTOM_CHANGELOG.md
+changelog neuropoly/spinalcordtoolbox --update --name CUSTOM_CHANGELOG.md
+
+# run in debug
+changelog neuropoly/spinalcordtoolbox --log-level DEBUG
+```
+
 To use a Github Personal Access Token (https://github.com/settings/tokens) simply export the token string via the `GITHUB_TOKEN` environment variable.
 
-The script will produce a `[user]_[repo]_changelog.[tagId].md` file with changelog contents. The contents can then be verified manually and copied over to the respective project `CHANGES.md` file.
+Unless `--update` is passed, the script will produce a `[user]_[repo]_changelog.[tagId].md` file with changelog contents.
 
 Contributions are welcome (via a fork of the repository and pull request) 🎉
diff --git a/changelog/changelog.py b/changelog/changelog.py
index daf67cb..7e9f443 100755
--- a/changelog/changelog.py
+++ b/changelog/changelog.py
@@ -188,6 +188,16 @@ def get_parser():
         help="Logging level (eg. INFO, see Python logging docs)",
     )
 
+    optional.add_argument("--update",
+        action='store_true',
+        help="Update an existing changelog file by prepending to it.",
+    )
+
+    optional.add_argument("--name",
+        type=str,
+        default='CHANGES.md',
+        help="Existing changelog file to use.",
+    )
 
     return parser
 
@@ -229,10 +239,35 @@ def main():
     for diff in diff_pr:
         logger.warning('Pull request not labeled: %s', diff)
 
-    filename = f"{user}_{repo}_changelog.{milestone['number']}.md"
-    with io.open(filename, "w") as changelog:
-        changelog.write('\n'.join(lines))
-    logger.info(f"Changelog saved in {filename}")
+    if args.update:
+        filename = args.name
+        if not os.path.exists(filename):
+            raise IOError(f"The provided changelog file: {filename} does not exist!")
+
+        with io.open(filename, 'r') as f:
+            original = f.readlines()
+
+        backup = f"{filename}.bak"
+        os.rename(filename, backup)
+
+        with io.open(filename, 'w') as changelog:
+            # re-use first line from existing file since it most likely contains the title
+            changelog.write(original[0] + '\n')
+
+            # write current changelog
+            changelog.write('\n'.join(lines))
+
+            # write back rest of changelog
+            changelog.writelines(original)
+
+        logger.info(f"Backup created: {backup}")
+
+    else:
+        filename = f"{user}_{repo}_changelog.{milestone['number']}.md"
+        with io.open(filename, "w") as changelog:
+            changelog.write('\n'.join(lines))
+
+    logger.info(f"Changelog written into {filename}")
 
 
 # provides customization to changelog for some repos