diff --git a/src/command.ts b/src/command.ts
index e0c7316..8e36d69 100644
--- a/src/command.ts
+++ b/src/command.ts
@@ -4,6 +4,7 @@ import { CLIError, resolveValue, toArray } from "./_utils.ts";
 import { parseArgs } from "./args.ts";
 import { cyan } from "./_color.ts";
 import { resolvePlugins } from "./plugin.ts";
+import { validateUnknownOptions } from "./validate.ts";
 
 export function defineCommand<const T extends ArgsDef = ArgsDef>(
   def: CommandDef<T>,
@@ -21,6 +22,7 @@ export async function runCommand<T extends ArgsDef = ArgsDef>(
   cmd: CommandDef<T>,
   opts: RunCommandOptions,
 ): Promise<{ result: unknown }> {
+  const cmdMeta = await resolveValue(cmd.meta);
   const cmdArgs = await resolveValue(cmd.args || {});
   const parsedArgs = parseArgs<T>(opts.rawArgs, cmdArgs);
 
@@ -35,6 +37,7 @@ export async function runCommand<T extends ArgsDef = ArgsDef>(
   const plugins = await resolvePlugins(cmd.plugins ?? []);
 
   let result: unknown;
+  let handledBySubCommand = false;
   let runError: unknown;
   try {
     // Plugin setup hooks
@@ -58,6 +61,7 @@ export async function runCommand<T extends ArgsDef = ArgsDef>(
         if (!subCommand) {
           throw new CLIError(`Unknown command ${cyan(explicitName)}`, "E_UNKNOWN_COMMAND");
         }
+        handledBySubCommand = true;
         await runCommand(subCommand, {
           rawArgs: opts.rawArgs.slice(subCommandArgIndex + 1),
         });
@@ -78,6 +82,7 @@ export async function runCommand<T extends ArgsDef = ArgsDef>(
               "E_UNKNOWN_COMMAND",
             );
           }
+          handledBySubCommand = true;
           await runCommand(subCommand, {
             rawArgs: opts.rawArgs,
           });
@@ -87,6 +92,11 @@ export async function runCommand<T extends ArgsDef = ArgsDef>(
       }
     }
 
+    // Validate unknown options (skip if handled by sub command)
+    if (!handledBySubCommand && !cmdMeta?.allowUnknownOptions) {
+      validateUnknownOptions(cmdArgs, parsedArgs);
+    }
+
     // Handle main command
     if (typeof cmd.run === "function") {
       result = await cmd.run(context);
diff --git a/src/types.ts b/src/types.ts
index e4280ef..da9ee82 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -90,6 +90,7 @@ export interface CommandMeta {
   description?: string;
   hidden?: boolean;
   alias?: string | string[];
+  allowUnknownOptions?: boolean;
 }
 
 // Command: Definition
diff --git a/src/validate.ts b/src/validate.ts
new file mode 100644
index 0000000..30e6279
--- /dev/null
+++ b/src/validate.ts
@@ -0,0 +1,26 @@
+import { CLIError, toArray } from "./_utils.ts";
+import type { ArgsDef, ParsedArgs } from "./types.ts";
+
+export function validateUnknownOptions<T extends ArgsDef = ArgsDef>(
+  argsDef: T,
+  args: ParsedArgs<T>,
+): void {
+  const names = new Set<string>();
+  for (const [name, argDef] of Object.entries(argsDef || {})) {
+    names.add(name);
+    for (const alias of toArray((argDef as any).alias)) {
+      names.add(alias);
+    }
+  }
+
+  for (const arg of Object.keys(args)) {
+    if (arg === "_") continue;
+
+    if (!names.has(arg)) {
+      throw new CLIError(
+        `Unknown option \`${arg.length > 1 ? `--${arg}` : `-${arg}`}\``,
+        "E_UNKNOWN_OPTION",
+      );
+    }
+  }
+}
diff --git a/test/main.test.ts b/test/main.test.ts
index 13cc609..3de20c0 100644
--- a/test/main.test.ts
+++ b/test/main.test.ts
@@ -1,4 +1,4 @@
-import { describe, it, expect, vi, afterAll } from "vitest";
+import { describe, it, expect, vi, afterEach } from "vitest";
 import { createMain, defineCommand, renderUsage, runMain, showUsage } from "../src/index.ts";
 import * as commandModule from "../src/command.ts";
 
@@ -9,8 +9,9 @@ describe("runMain", () => {
 
   const consoleErrorMock = vi.spyOn(console, "error").mockImplementation(() => undefined);
 
-  afterAll(() => {
+  afterEach(() => {
     consoleMock.mockReset();
+    consoleErrorMock.mockReset();
   });
 
   it("shows version with flag `--version`", async () => {
@@ -102,6 +103,39 @@ describe("runMain", () => {
     await runMain(command, { rawArgs });
 
     expect(mockRunCommand).toHaveBeenCalledWith(command, { rawArgs });
+    expect(consoleErrorMock).toHaveBeenCalledWith("Unknown option `--foo`");
+  });
+
+  it("should not warn for subcommand options", async () => {
+    const command = defineCommand({
+      subCommands: {
+        foo: {
+          args: {
+            bar: { type: "string" },
+          },
+          run: () => {},
+        },
+      },
+    });
+
+    await runMain(command, { rawArgs: ["foo", "--bar", "baz"] });
+
+    expect(consoleErrorMock).not.toHaveBeenCalled();
+  });
+
+  it("should allow unknown options with `allowUnknownOptions` enabled", async () => {
+    const mockRunCommand = vi.spyOn(commandModule, "runCommand");
+
+    const command = defineCommand({
+      meta: { allowUnknownOptions: true },
+    });
+
+    const rawArgs = ["--foo", "bar"];
+
+    await runMain(command, { rawArgs });
+
+    expect(mockRunCommand).toHaveBeenCalledWith(command, { rawArgs });
+    expect(consoleErrorMock).not.toHaveBeenCalledWith("Unknown option `--foo`");
   });
 });