diff --git a/src/main/main.ts b/src/main/main.ts
index 1a45778..37c775f 100644
--- a/src/main/main.ts
+++ b/src/main/main.ts
@@ -20,6 +20,12 @@ const mainDashboardUrl = `http://localhost:${appConfig.nodecgPort}/bundles/${app
 const loadingDashboardUrl = `http://localhost:${appConfig.nodecgPort}/bundles/${appConfig.bundleName}/${appConfig.loadingDashboardRoute}`;
 const nodecgBaseUrl = `http://127.0.0.1:${appConfig.nodecgPort}`;
 
+const hasSingleInstanceLock = app.requestSingleInstanceLock();
+
+if (!hasSingleInstanceLock) {
+  app.quit();
+}
+
 const nodecgManager = createNodecgProcessManager({
   isDev,
   nodecgRootPath,
@@ -34,6 +40,21 @@ let mainWindow: BrowserWindow | null = null;
 let loadingWindow: BrowserWindow | null = null;
 let shutdownState: AppShutdownState = "running";
 
+function focusExistingWindow(): void {
+  const targetWindow = mainWindow && !mainWindow.isDestroyed() ? mainWindow : loadingWindow;
+
+  if (!targetWindow || targetWindow.isDestroyed()) {
+    return;
+  }
+
+  if (targetWindow.isMinimized()) {
+    targetWindow.restore();
+  }
+
+  targetWindow.show();
+  targetWindow.focus();
+}
+
 async function launchApplication(): Promise<void> {
   // We create both windows early so startup feels instant while NodeCG is booting in the background.
   mainWindow = createMainWindow({ appConfig, rootPath, mainDashboardUrl });
@@ -100,6 +121,10 @@ function stopNodecgGracefully(): Promise<void> {
 }
 
 app.on("ready", () => {
+  if (!hasSingleInstanceLock) {
+    return;
+  }
+
   if (process.platform === "win32") {
     app.setAppUserModelId(appConfig.userModelId);
   }
@@ -111,6 +136,10 @@ app.on("ready", () => {
   });
 });
 
+app.on("second-instance", () => {
+  focusExistingWindow();
+});
+
 app.on("activate", async () => {
   if (BrowserWindow.getAllWindows().length === 0) {
     mainWindow = createMainWindow({ appConfig, rootPath, mainDashboardUrl });