diff --git a/packages/rspack-cli/src/cli.ts b/packages/rspack-cli/src/cli.ts
index 501ce04cea17..f1c38faacbeb 100644
--- a/packages/rspack-cli/src/cli.ts
+++ b/packages/rspack-cli/src/cli.ts
@@ -1,3 +1,4 @@
+import fs from 'node:fs';
 import path from 'node:path';
 import util from 'node:util';
 import type {
@@ -71,6 +72,11 @@ function createAnsiFormatter(
   };
 }
 
+const hasDefaultEntry = (context: string) =>
+  ['./src', './src.js', './src.json'].some((request) =>
+    fs.existsSync(path.resolve(context, request)),
+  );
+
 export class RspackCLI {
   colors: RspackCLIColors;
   program: CAC;
@@ -207,6 +213,7 @@ export class RspackCLI {
     const isServe = command === 'serve';
 
     const internalBuildConfig = async (item: RspackOptions) => {
+      const configPaths = pathMap.get(item);
       if (options.entry) {
         item.entry = {
           main: options.entry.map((x) => path.resolve(process.cwd(), x))[0], // Fix me when entry supports array
@@ -248,6 +255,17 @@ export class RspackCLI {
       }
 
       if (isServe) {
+        if (
+          !configPaths &&
+          !options.entry &&
+          !item.entry &&
+          !hasDefaultEntry(item.context ?? process.cwd())
+        ) {
+          this.getLogger().warn(
+            "No rspack config found and default entry './src' does not exist. `rspack serve` starts a development compilation. To serve production build output, use `rspack preview [dir]`.",
+          );
+        }
+
         const installed = (item.plugins ||= []).find(
           (item) => item instanceof rspack.ProgressPlugin,
         );
@@ -262,7 +280,6 @@ export class RspackCLI {
         typeof cacheOptions === 'object' &&
         cacheOptions.type === 'persistent'
       ) {
-        const configPaths = pathMap.get(item);
         if (configPaths) {
           // for persistent cache
           cacheOptions.buildDependencies = [
diff --git a/packages/rspack-cli/tests/serve/missing-default-entry/index.test.ts b/packages/rspack-cli/tests/serve/missing-default-entry/index.test.ts
new file mode 100644
index 000000000000..245a865ece7e
--- /dev/null
+++ b/packages/rspack-cli/tests/serve/missing-default-entry/index.test.ts
@@ -0,0 +1,20 @@
+import {
+  normalizeStderr,
+  runWatch,
+  uniqueDirectoryForTest,
+} from '../../utils/test-utils';
+
+describe('serve without a config or default entry', () => {
+  it('suggests preview when serving build output may be intended', async () => {
+    const cwd = await uniqueDirectoryForTest();
+    const { stdout, stderr } = await runWatch(cwd, ['serve'], {
+      killString: /Module not found|rspack preview \[dir\]/,
+    });
+
+    const output = normalizeStderr(`${stdout}\n${stderr}`);
+    expect(output).toContain(
+      "No rspack config found and default entry './src' does not exist.",
+    );
+    expect(output).toContain('use `rspack preview [dir]`');
+  });
+});