diff --git a/packages/vitest/src/config.ts b/packages/vitest/src/config.ts
index 0afb83cccd86..1fdd469cd2bf 100644
--- a/packages/vitest/src/config.ts
+++ b/packages/vitest/src/config.ts
@@ -10,13 +10,19 @@ export { configDefaults, defaultInclude, defaultExclude, coverageConfigDefaults
 export { mergeConfig } from 'vite'
 
 export type { ConfigEnv, ViteUserConfig as UserConfig }
+export type UserConfigFnObject = (env: ConfigEnv) => ViteUserConfig
+export type UserConfigFnPromise = (env: ConfigEnv) => Promise<ViteUserConfig>
 export type UserConfigFn = (env: ConfigEnv) => ViteUserConfig | Promise<ViteUserConfig>
-export type UserConfigExport = ViteUserConfig | Promise<ViteUserConfig> | UserConfigFn
+export type UserConfigExport = ViteUserConfig | Promise<ViteUserConfig> | UserConfigFnObject | UserConfigFnPromise | UserConfigFn
 
 export type UserProjectConfigFn = (env: ConfigEnv) => UserWorkspaceConfig | Promise<UserWorkspaceConfig>
 export type UserProjectConfigExport = UserWorkspaceConfig | Promise<UserWorkspaceConfig> | UserProjectConfigFn
 
-export function defineConfig(config: UserConfigExport) {
+export function defineConfig(config: ViteUserConfig): ViteUserConfig
+export function defineConfig(config: Promise<ViteUserConfig>): Promise<ViteUserConfig>
+export function defineConfig(config: UserConfigFnObject): UserConfigFnObject
+export function defineConfig(config: UserConfigExport): UserConfigExport
+export function defineConfig(config: UserConfigExport): UserConfigExport {
   return config
 }