diff --git a/README.md b/README.md
index 3f4401b..92c24fe 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,8 @@ See [action.yml](action.yml)
     # Can be 'space-delimited', 'csv', or 'json'.
     # Default: 'space-delimited'
     format: ''
+    # Filter files using a regex
+    filter: '*'
 ```
 
 # Scenarios
@@ -36,6 +38,8 @@ Consider using one of the other formats if that's the case.
 ```yaml
 - id: files
   uses: jitterbit/get-changed-files@v1
+  with:
+    filter: '*.php'
 - run: |
     for changed_file in ${{ steps.files.outputs.all }}; do
       echo "Do something with this ${changed_file}."
diff --git a/dist/index.js b/dist/index.js
index 72c1662..85fc9d6 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -3517,6 +3517,7 @@ function run() {
             // Create GitHub client with the API token.
             const client = new github_1.GitHub(core.getInput('token', { required: true }));
             const format = core.getInput('format', { required: true });
+            const filter = core.getInput('filter', { required: true }) || '*';
             // Ensure that the format parameter is set properly.
             if (format !== 'space-delimited' && format !== 'csv' && format !== 'json') {
                 core.setFailed(`Format must be one of 'string-delimited', 'csv', or 'json', got '${format}'.`);
@@ -3570,8 +3571,9 @@ function run() {
                 core.setFailed(`The head commit for this ${github_1.context.eventName} event is not ahead of the base commit. ` +
                     "Please submit an issue on this action's GitHub repo.");
             }
+            const regex = new RegExp(`/${filter}\\b`, 'g');
             // Get the changed files from the response payload.
-            const files = response.data.files;
+            const files = response.data.files.filter(file => file.filename.match(regex));
             const all = [], added = [], modified = [], removed = [], renamed = [], addedModified = [];
             for (const file of files) {
                 const filename = file.filename;
diff --git a/src/main.ts b/src/main.ts
index 0f0fdd6..c37750a 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -9,6 +9,7 @@ async function run(): Promise<void> {
     // Create GitHub client with the API token.
     const client = new GitHub(core.getInput('token', {required: true}))
     const format = core.getInput('format', {required: true}) as Format
+    const filter = core.getInput('filter', {required: true}) || '*'
 
     // Ensure that the format parameter is set properly.
     if (format !== 'space-delimited' && format !== 'csv' && format !== 'json') {
@@ -82,8 +83,9 @@ async function run(): Promise<void> {
       )
     }
 
+    const regex = new RegExp(`/${filter}\\b`, 'g')
     // Get the changed files from the response payload.
-    const files = response.data.files
+    const files = response.data.files.filter(file => file.filename.match(regex))
     const all = [] as string[],
       added = [] as string[],
       modified = [] as string[],