diff --git a/.changeset/big-months-deliver.md b/.changeset/big-months-deliver.md
new file mode 100644
index 0000000000..1cf873beb1
--- /dev/null
+++ b/.changeset/big-months-deliver.md
@@ -0,0 +1,5 @@
+---
+'@backstage/cli': patch
+---
+
+Added `--since <ref>` flag for `repo build` command.`
diff --git a/packages/cli/src/commands/index.ts b/packages/cli/src/commands/index.ts
index d3baa37b3f..5cb02c82b4 100644
--- a/packages/cli/src/commands/index.ts
+++ b/packages/cli/src/commands/index.ts
@@ -41,6 +41,10 @@ export function registerRepoCommand(program: CommanderStatic) {
       '--all',
       'Build all packages, including bundled app and backend packages.',
     )
+    .option(
+      '--since <ref>',
+      'Only build packages and their dev dependents that changed since the specified ref',
+    )
     .action(lazy(() => import('./repo/build').then(m => m.command)));
 
   command
diff --git a/packages/cli/src/commands/repo/build.ts b/packages/cli/src/commands/repo/build.ts
index ceb468ebfa..fe50bee84f 100644
--- a/packages/cli/src/commands/repo/build.ts
+++ b/packages/cli/src/commands/repo/build.ts
@@ -78,7 +78,18 @@ function createScriptOptionsParser(anyCmd: Command, commandPath: string[]) {
 }
 
 export async function command(cmd: Command): Promise<void> {
-  const packages = await PackageGraph.listTargetPackages();
+  let packages = await PackageGraph.listTargetPackages();
+
+  if (cmd.since) {
+    const graph = PackageGraph.fromPackages(packages);
+    const changedPackages = await graph.listChangedPackages({ ref: cmd.since });
+    const withDevDependents = graph.collectPackageNames(
+      changedPackages.map(pkg => pkg.name),
+      pkg => pkg.localDevDependents.keys(),
+    );
+    packages = Array.from(withDevDependents).map(name => graph.get(name)!);
+  }
+
   const apps = new Array<ExtendedPackage>();
   const backends = new Array<ExtendedPackage>();