diff --git chrome/browser/themes/theme_service.cc chrome/browser/themes/theme_service.cc
index e49552e272e4..b935ef2d47b9 100644
--- chrome/browser/themes/theme_service.cc
+++ chrome/browser/themes/theme_service.cc
@@ -26,6 +26,7 @@
 #include "base/task/thread_pool.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
+#include "cef/libcef/features/runtime.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/theme_installed_infobar_delegate.h"
@@ -55,6 +56,10 @@
 #include "extensions/common/extension_set.h"
 #include "ui/base/layout.h"
 
+#if BUILDFLAG(ENABLE_CEF)
+#include "cef/libcef/common/extensions/extensions_util.h"
+#endif
+
 #if BUILDFLAG(ENABLE_EXTENSIONS)
 #include "base/scoped_observer.h"
 #include "extensions/browser/extension_registry_observer.h"
@@ -271,11 +276,19 @@ void ThemeService::Init() {
   // OnExtensionServiceReady. Otherwise, the ThemeObserver won't be
   // constructed in time to observe the corresponding events.
 #if BUILDFLAG(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_CEF)
+  const bool extensions_disabled = cef::IsAlloyRuntimeEnabled() &&
+                                   !extensions::ExtensionsEnabled();
+#else
+  const bool extensions_disabled = false;
+#endif
+  if (!extensions_disabled) {
   theme_observer_ = std::make_unique<ThemeObserver>(this);
 
   extensions::ExtensionSystem::Get(profile_)->ready().Post(
       FROM_HERE, base::Bind(&ThemeService::OnExtensionServiceReady,
                             weak_ptr_factory_.GetWeakPtr()));
+  }
 #endif
   theme_syncable_service_.reset(new ThemeSyncableService(profile_, this));
 
diff --git chrome/browser/themes/theme_service_factory.cc chrome/browser/themes/theme_service_factory.cc
index caec77bbe3ba..92a813acc008 100644
--- chrome/browser/themes/theme_service_factory.cc
+++ chrome/browser/themes/theme_service_factory.cc
@@ -6,6 +6,7 @@
 
 #include "base/no_destructor.h"
 #include "build/build_config.h"
+#include "cef/libcef/features/runtime.h"
 #include "chrome/browser/extensions/extension_system_factory.h"
 #include "chrome/browser/profiles/incognito_helpers.h"
 #include "chrome/browser/profiles/profile.h"
@@ -27,6 +28,10 @@
 #include "ui/views/linux_ui/linux_ui.h"
 #endif
 
+#if BUILDFLAG(ENABLE_CEF)
+#include "cef/libcef/common/extensions/extensions_util.h"
+#endif
+
 namespace {
 
 const ThemeHelper& GetThemeHelper() {
@@ -70,7 +75,15 @@ ThemeServiceFactory::ThemeServiceFactory()
           BrowserContextDependencyManager::GetInstance()) {
   DependsOn(extensions::ExtensionRegistryFactory::GetInstance());
   DependsOn(extensions::ExtensionPrefsFactory::GetInstance());
+#if BUILDFLAG(ENABLE_CEF)
+  const bool extensions_disabled = cef::IsAlloyRuntimeEnabled() &&
+                                   !extensions::ExtensionsEnabled();
+#else
+  const bool extensions_disabled = false;
+#endif
+  if (!extensions_disabled) {
   DependsOn(extensions::ExtensionSystemFactory::GetInstance());
+  }
 }
 
 ThemeServiceFactory::~ThemeServiceFactory() {}