diff --git a/pr-sync/action.yml b/pr-sync/action.yml
index b6074ad..7aeb979 100644
--- a/pr-sync/action.yml
+++ b/pr-sync/action.yml
@@ -15,7 +15,7 @@ inputs:
     required: true
   project-id:
     description: The ID of the project board to sync PRs towards
-    required: true
+    required: false
   excluded-users:
     description: A comma separated list of usernames of users that should not be assigned PRs
     required: false
diff --git a/pr-sync/index.ts b/pr-sync/index.ts
index 35d263c..3e83359 100644
--- a/pr-sync/index.ts
+++ b/pr-sync/index.ts
@@ -20,7 +20,7 @@ async function main() {
     `PR sync #${issueNumber} ${eventName}/${action} actor=${actor} author=${author}`,
   );
 
-  const projectId = core.getInput('project-id', { required: true });
+  const projectId = core.getInput('project-id', { required: false });
   const excludedUsers = core.getInput('excluded-users', { required: false });
   const owningTeams = core.getInput('owning-teams', { required: false });
   const token = core.getInput('github-token', { required: true });
diff --git a/pr-sync/syncProjectBoard.ts b/pr-sync/syncProjectBoard.ts
index acd7a6a..9a2cc31 100644
--- a/pr-sync/syncProjectBoard.ts
+++ b/pr-sync/syncProjectBoard.ts
@@ -30,6 +30,11 @@ export async function syncProjectBoard(
   options: Options,
   log = core.info,
 ) {
+  if (!options.projectId) {
+    log('No project ID provided, skipping project board sync');
+    return;
+  }
+
   if (options.eventName === 'pull_request_target') {
     if (['opened', 'reopened'].includes(options.action!)) {
       await addToBoard(client, options, log);