diff --git a/electron/main.ts b/electron/main.ts
index 89a4814..1d9bacf 100644
--- a/electron/main.ts
+++ b/electron/main.ts
@@ -5,6 +5,17 @@ import { fileURLToPath } from "node:url";
 
 const __dirname = path.dirname(fileURLToPath(import.meta.url));
 
+const titleBarThemes = {
+  light: {
+    color: "#eef1ed",
+    symbolColor: "#17241d"
+  },
+  dark: {
+    color: "#132019",
+    symbolColor: "#e9f3ec"
+  }
+};
+
 async function createWindow() {
   const win = new BrowserWindow({
     width: 1220,
@@ -14,8 +25,7 @@ async function createWindow() {
     title: "EnvHelper",
     titleBarStyle: "hidden",
     titleBarOverlay: {
-      color: "#eef1ed",
-      symbolColor: "#17241d",
+      ...titleBarThemes.light,
       height: 34
     },
     autoHideMenuBar: true,
@@ -53,6 +63,13 @@ ipcMain.handle("envhelper:open-file", async () => {
   };
 });
 
+ipcMain.handle("envhelper:set-titlebar-theme", (event, theme: "light" | "dark") => {
+  BrowserWindow.fromWebContents(event.sender)?.setTitleBarOverlay({
+    ...titleBarThemes[theme],
+    height: 34
+  });
+});
+
 ipcMain.handle("envhelper:save-file", async (_event, content: string) => {
   const result = await dialog.showSaveDialog({
     defaultPath: ".env",
diff --git a/electron/preload.ts b/electron/preload.ts
index cf5fa72..2e13e96 100644
--- a/electron/preload.ts
+++ b/electron/preload.ts
@@ -2,5 +2,6 @@ import { contextBridge, ipcRenderer } from "electron";
 
 contextBridge.exposeInMainWorld("envHelper", {
   openFile: () => ipcRenderer.invoke("envhelper:open-file"),
-  saveFile: (content: string) => ipcRenderer.invoke("envhelper:save-file", content)
+  saveFile: (content: string) => ipcRenderer.invoke("envhelper:save-file", content),
+  setTitlebarTheme: (theme: "light" | "dark") => ipcRenderer.invoke("envhelper:set-titlebar-theme", theme)
 });
diff --git a/src/App.tsx b/src/App.tsx
index 63938b1..f60d5c6 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -271,6 +271,14 @@ function readTheme(): ThemeMode {
   return stored && themeLabels.includes(stored) ? stored : "system";
 }
 
+function getEffectiveTheme(themeMode: ThemeMode): "light" | "dark" {
+  if (themeMode !== "system") {
+    return themeMode;
+  }
+
+  return window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light";
+}
+
 export default function App() {
   const [input, setInput] = useState(sampleEnv);
   const [loadedPath, setLoadedPath] = useState<string | null>(null);
@@ -286,6 +294,16 @@ export default function App() {
   useEffect(() => {
     document.documentElement.dataset.theme = themeMode;
     localStorage.setItem("envhelper-theme", themeMode);
+
+    const updateTitlebar = () => {
+      void window.envHelper?.setTitlebarTheme(getEffectiveTheme(themeMode));
+    };
+    const media = window.matchMedia("(prefers-color-scheme: dark)");
+
+    updateTitlebar();
+    media.addEventListener("change", updateTitlebar);
+
+    return () => media.removeEventListener("change", updateTitlebar);
   }, [themeMode]);
 
   useEffect(() => {
diff --git a/src/vite-env.d.ts b/src/vite-env.d.ts
index d1c7072..6c2aa67 100644
--- a/src/vite-env.d.ts
+++ b/src/vite-env.d.ts
@@ -9,5 +9,6 @@ interface Window {
   envHelper?: {
     openFile: () => Promise<EnvHelperFileResult | null>;
     saveFile: (content: string) => Promise<string | null>;
+    setTitlebarTheme: (theme: "light" | "dark") => Promise<void>;
   };
 }