diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3672772665..da2116bf54 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@
 - Enhance: 絵文字ピッカーのサイズをより大きくできるように
 - Enhance: 時刻計算のための基準値を一か所で管理するようにし、パフォーマンスを向上
 - Fix: iOSで、デバイスがダークモードだと初回読み込み時にエラーになる問題を修正
+- Fix: 設定データの移行が完了しているクライアントでは、設定データ移行用のプログラムの読み込みをスキップするように
 
 ### Server
 - Enhance: ユーザーIPを確実に取得できるために設定ファイルにFastifyOptions.trustProxyを追加しました
diff --git a/packages/frontend/src/boot/main-boot.ts b/packages/frontend/src/boot/main-boot.ts
index 18817d3f79..6fea9122ad 100644
--- a/packages/frontend/src/boot/main-boot.ts
+++ b/packages/frontend/src/boot/main-boot.ts
@@ -27,7 +27,6 @@ import { makeHotkey } from '@/utility/hotkey.js';
 import { addCustomEmoji, removeCustomEmojis, updateCustomEmojis } from '@/custom-emojis.js';
 import { prefer } from '@/preferences.js';
 import { updateCurrentAccountPartial } from '@/accounts.js';
-import { migrateOldSettings } from '@/pref-migrate.js';
 import { unisonReload } from '@/utility/unison-reload.js';
 
 export async function mainBoot() {
@@ -74,6 +73,8 @@ export async function mainBoot() {
 		if (lastVersion && (compareVersions('2025.3.2-alpha.0', lastVersion) === 1)) {
 			console.log('Preferences migration');
 
+			const { migrateOldSettings } = await import('@/pref-migrate.js');
+
 			migrateOldSettings();
 		}
 	}
diff --git a/packages/frontend/src/pref-migrate.ts b/packages/frontend/src/pref-migrate.ts
index 8258bbb846..d3cc0961b1 100644
--- a/packages/frontend/src/pref-migrate.ts
+++ b/packages/frontend/src/pref-migrate.ts
@@ -14,15 +14,23 @@ import * as os from '@/os.js';
 import { i18n } from '@/i18n.js';
 
 // TODO: そのうち消す
-export function migrateOldSettings() {
+export async function migrateOldSettings() {
 	os.waiting({ text: i18n.ts.settingsMigrating });
 
-	store.loaded.then(async () => {
-		misskeyApi('i/registry/get', { scope: ['client'], key: 'themes' }).catch(() => []).then((themes: any) => {
+	const minWait = new Promise<void>(resolve => {
+		window.setTimeout(() => {
+			resolve();
+		}, 5000);
+	});
+
+	const migratePromise = store.loaded.then(async () => {
+		const migrationPromises: Promise<any>[] = [];
+
+		migrationPromises.push(misskeyApi('i/registry/get', { scope: ['client'], key: 'themes' }).catch(() => []).then((themes: any) => {
 			if (themes.length > 0) {
 				prefer.commit('themes', themes);
 			}
-		});
+		}));
 
 		const plugins = ColdDeviceStorage.get('plugins');
 		prefer.commit('plugins', plugins.map(p => {
@@ -35,7 +43,7 @@ export function migrateOldSettings() {
 		}));
 
 		prefer.commit('deck.profile', deckStore.s.profile);
-		misskeyApi('i/registry/keys', {
+		migrationPromises.push(misskeyApi('i/registry/keys', {
 			scope: ['client', 'deck', 'profiles'],
 		}).then(async keys => {
 			const profiles: DeckProfile[] = [];
@@ -52,7 +60,7 @@ export function migrateOldSettings() {
 				});
 			}
 			prefer.commit('deck.profiles', profiles);
-		});
+		}));
 
 		prefer.commit('lightTheme', ColdDeviceStorage.get('lightTheme'));
 		prefer.commit('darkTheme', ColdDeviceStorage.get('darkTheme'));
@@ -146,8 +154,11 @@ export function migrateOldSettings() {
 		prefer.commit('defaultNoteVisibility', store.s.defaultNoteVisibility);
 		prefer.commit('defaultNoteLocalOnly', store.s.defaultNoteLocalOnly);
 
-		window.setTimeout(() => {
-			unisonReload();
-		}, 10000);
+		await Promise.all(migrationPromises);
 	});
+
+	// 最低5秒 or 設定移行が完了するまで待つ
+	await Promise.all([migratePromise, minWait]);
+
+	unisonReload();
 }