diff --git a/packages/core/src/config.ts b/packages/core/src/config.ts
index 9e968d379..ffca44347 100644
--- a/packages/core/src/config.ts
+++ b/packages/core/src/config.ts
@@ -879,13 +879,23 @@ export const appendEntryQuery = (entries: RsbuildConfigEntry): RsbuildEntry =>
   traverseEntryQuery(entries, (item) => `${item}?${RSLIB_ENTRY_QUERY}`);
 
 const composeEntryConfig = async (
-  entries: RsbuildConfigEntry,
+  rawEntry: RsbuildConfigEntry,
   bundle: LibConfig['bundle'],
   root: string,
   cssModulesAuto: CssLoaderOptionsAuto,
 ): Promise<{ entryConfig: EnvironmentConfig; lcp: string | null }> => {
+  let entries = rawEntry;
+
   if (!entries) {
-    return { entryConfig: {}, lcp: null };
+    // In bundle mode, return directly to let Rsbuild apply default entry to './src/index.ts'
+    if (bundle !== false) {
+      return { entryConfig: {}, lcp: null };
+    }
+
+    // In bundleless mode, set default entry to './src/**'
+    entries = {
+      index: 'src/**',
+    };
   }
 
   if (bundle !== false) {
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index ef57ed520..2fcecb65e 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -660,6 +660,8 @@ importers:
 
   tests/integration/dts/composite/process-files: {}
 
+  tests/integration/entry/default: {}
+
   tests/integration/entry/glob: {}
 
   tests/integration/entry/glob-bundle: {}
diff --git a/tests/integration/entry/default/package.json b/tests/integration/entry/default/package.json
new file mode 100644
index 000000000..867565910
--- /dev/null
+++ b/tests/integration/entry/default/package.json
@@ -0,0 +1,6 @@
+{
+  "name": "entry-default-test",
+  "version": "1.0.0",
+  "private": true,
+  "type": "module"
+}
diff --git a/tests/integration/entry/default/rslib.config.ts b/tests/integration/entry/default/rslib.config.ts
new file mode 100644
index 000000000..789f486d0
--- /dev/null
+++ b/tests/integration/entry/default/rslib.config.ts
@@ -0,0 +1,37 @@
+import { defineConfig } from '@rslib/core';
+import { generateBundleCjsConfig, generateBundleEsmConfig } from 'test-helper';
+
+export default defineConfig({
+  lib: [
+    generateBundleEsmConfig({
+      output: {
+        distPath: {
+          root: 'dist/esm-bundle',
+        },
+      },
+    }),
+    generateBundleCjsConfig({
+      output: {
+        distPath: {
+          root: 'dist/cjs-bundle',
+        },
+      },
+    }),
+    generateBundleEsmConfig({
+      output: {
+        distPath: {
+          root: 'dist/esm-bundle-false',
+        },
+      },
+      bundle: false,
+    }),
+    generateBundleCjsConfig({
+      output: {
+        distPath: {
+          root: 'dist/cjs-bundle-false',
+        },
+      },
+      bundle: false,
+    }),
+  ],
+});
diff --git a/tests/integration/entry/default/src/foo.ts b/tests/integration/entry/default/src/foo.ts
new file mode 100644
index 000000000..3329a7d97
--- /dev/null
+++ b/tests/integration/entry/default/src/foo.ts
@@ -0,0 +1 @@
+export const foo = 'foo';
diff --git a/tests/integration/entry/default/src/index.ts b/tests/integration/entry/default/src/index.ts
new file mode 100644
index 000000000..3c8dc405f
--- /dev/null
+++ b/tests/integration/entry/default/src/index.ts
@@ -0,0 +1,3 @@
+import { foo } from './foo';
+
+export const text = () => `hello ${foo}`;
diff --git a/tests/integration/entry/index.test.ts b/tests/integration/entry/index.test.ts
index 571d8672c..81f78a432 100644
--- a/tests/integration/entry/index.test.ts
+++ b/tests/integration/entry/index.test.ts
@@ -3,6 +3,30 @@ import stripAnsi from 'strip-ansi';
 import { buildAndGetResults, queryContent } from 'test-helper';
 import { expect, test } from 'vitest';
 
+test('default entry', async () => {
+  const fixturePath = join(__dirname, 'default');
+  const { files } = await buildAndGetResults({ fixturePath });
+
+  expect(files).toMatchInlineSnapshot(`
+    {
+      "cjs0": [
+        "<ROOT>/tests/integration/entry/default/dist/cjs-bundle/index.cjs",
+      ],
+      "cjs1": [
+        "<ROOT>/tests/integration/entry/default/dist/cjs-bundle-false/foo.cjs",
+        "<ROOT>/tests/integration/entry/default/dist/cjs-bundle-false/index.cjs",
+      ],
+      "esm0": [
+        "<ROOT>/tests/integration/entry/default/dist/esm-bundle/index.js",
+      ],
+      "esm1": [
+        "<ROOT>/tests/integration/entry/default/dist/esm-bundle-false/foo.js",
+        "<ROOT>/tests/integration/entry/default/dist/esm-bundle-false/index.js",
+      ],
+    }
+  `);
+});
+
 test('single entry bundle', async () => {
   const fixturePath = join(__dirname, 'single');
   const { files } = await buildAndGetResults({ fixturePath });
diff --git a/website/docs/en/config/lib/bundle.mdx b/website/docs/en/config/lib/bundle.mdx
index 847fe7458..013e34e7b 100644
--- a/website/docs/en/config/lib/bundle.mdx
+++ b/website/docs/en/config/lib/bundle.mdx
@@ -19,7 +19,9 @@ We should specify the entry file for the build.
 
 ### bundle: true
 
-When `bundle` is set to `true`, the entry should be set to the entry file. The default entry is `src/index.(ts|js|tsx|jsx|mjs|cjs)`. You should make sure that the entry file exists, or customize entry through the [source.entry](https://rsbuild.dev/config/source/entry) configuration.
+When `bundle` is set to `true`, the entry should be set to the entry file. The default entry in bundle mode is `src/index.(ts|js|tsx|jsx|mjs|cjs)`. You should make sure that the entry file exists, or customize entry through the [source.entry](https://rsbuild.dev/config/source/entry) configuration.
+
+**Example:**
 
 ```ts title="rslib.config.ts"
 export default {
@@ -39,7 +41,9 @@ export default {
 
 ### bundle: false
 
-When `bundle` is set to `false`, the entry should be set a [glob pattern](https://github.com/micromatch/picomatch#globbing-features) to include all the files.
+When `bundle` is set to `false`, the entry should be set to a [glob pattern](https://github.com/micromatch/picomatch#globbing-features) to include all the files. The default entry in bundleless mode is `src/**`.
+
+**Example:**
 
 ```ts title="rslib.config.ts"
 export default {
@@ -51,7 +55,7 @@ export default {
   ],
   source: {
     entry: {
-      index: './src/**',
+      index: './foo/**',
     },
   },
 };
diff --git a/website/docs/en/config/rsbuild/source.mdx b/website/docs/en/config/rsbuild/source.mdx
index 574a4c8e6..fb202fd6b 100644
--- a/website/docs/en/config/rsbuild/source.mdx
+++ b/website/docs/en/config/rsbuild/source.mdx
@@ -19,10 +19,13 @@ Replaces variables in your code with other values or expressions at compile time
 
 ## source.entry <RsbuildDocBadge path="/config/source/entry" text="source.entry" />
 
-Used to set the entry modules for building.
+Used to set the entry modules for building. In Rslib, the default value of `source.entry` is:
+
+- bundle mode: `src/index.(ts|js|tsx|jsx|mjs|cjs)`
+- bundleless mode: `src/**`
 
 :::info
-Check out the [lib.bundle](/config/lib/bundle#set-entry) to learn how to set entry for bundle and bundleless project.
+Check out the [lib.bundle](/config/lib/bundle#set-entry) to learn more about how to set entry for bundle and bundleless project.
 :::
 
 ## source.exclude <RsbuildDocBadge path="/config/source/exclude" text="source.exclude" />
diff --git a/website/docs/zh/config/lib/bundle.mdx b/website/docs/zh/config/lib/bundle.mdx
index e612571f3..7ad91245a 100644
--- a/website/docs/zh/config/lib/bundle.mdx
+++ b/website/docs/zh/config/lib/bundle.mdx
@@ -6,7 +6,7 @@
 指定是否打包库，当 `bundle` 设置为 `true` 时称为 bundle 模式，设置为 `false` 时称为 bundleless 模式。更多详情请参见 [bundle / bundleless](/guide/basic/output-structure#bundle--bundleless)。
 
 ::: warning
-无打包模式尚未完全支持，某些功能如 [资源](/guide/advanced/assets) 可能无法正常工作。
+Bundleless 模式尚未完全支持，某些功能如 [资源](/guide/advanced/assets) 可能无法正常工作。
 :::
 
 ## 设置入口
@@ -15,7 +15,9 @@
 
 ### bundle: true
 
-当 `bundle` 设置为 `true` 时，入口需要设置为入口文件。默认入口为 `src/index.(ts|js|tsx|jsx|mjs|cjs)`。你需要确保入口文件存在，或通过 [source.entry](https://rsbuild.dev/zh/config/source/entry) 配置自定义入口。
+当 `bundle` 设置为 `true` 时，entry 需要设置为入口文件。Bundle 模式下的默认入口为 `src/index.(ts|js|tsx|jsx|mjs|cjs)`。你需要确保入口文件存在，或通过 [source.entry](https://rsbuild.dev/zh/config/source/entry) 配置自定义入口。
+
+**例子：**
 
 ```ts title="rslib.config.ts"
 export default {
@@ -35,7 +37,9 @@ export default {
 
 ### bundle: false
 
-当 `bundle` 设置为 `false` 时，入口需要设置为 [glob 模式](https://github.com/micromatch/picomatch#globbing-features) 以包含所有文件。
+当 `bundle` 设置为 `false` 时，入口需要设置为 [glob 模式](https://github.com/micromatch/picomatch#globbing-features) 以包含所有文件。Bundleless 模式下的默认入口为 `src/**`。
+
+**例子：**
 
 ```ts title="rslib.config.ts"
 export default {
@@ -47,7 +51,7 @@ export default {
   ],
   source: {
     entry: {
-      index: './src/**',
+      index: './foo/**',
     },
   },
 };
diff --git a/website/docs/zh/config/rsbuild/source.mdx b/website/docs/zh/config/rsbuild/source.mdx
index de59ba7b3..878ad7317 100644
--- a/website/docs/zh/config/rsbuild/source.mdx
+++ b/website/docs/zh/config/rsbuild/source.mdx
@@ -18,10 +18,13 @@ import { RsbuildDocBadge } from '@components/RsbuildDocBadge';
 
 ## source.entry <RsbuildDocBadge path="/config/source/entry" text="source.entry" />
 
-用于设置构建的入口模块。
+用于设置构建的入口模块。在 Rslib 中，`source.entry` 的默认值为：
+
+- bundle 模式：`src/index.(ts|js|tsx|jsx|mjs|cjs)`
+- bundleless 模式：`src/**`
 
 :::info
-参考 [lib.bundle](/config/lib/bundle#set-entry) 了解如何为 bundle 和 bundleless 项目设置入口。
+参考 [lib.bundle](/config/lib/bundle#set-entry) 进一步了解如何为 bundle 和 bundleless 项目设置入口。
 :::
 
 ## source.exclude <RsbuildDocBadge path="/config/source/exclude" text="source.exclude" />