diff --git a/checkbox/internal/checkbox.ts b/checkbox/internal/checkbox.ts
index 21a8ee03b5..d3f64f724a 100644
--- a/checkbox/internal/checkbox.ts
+++ b/checkbox/internal/checkbox.ts
@@ -23,7 +23,10 @@ import {
   getValidityAnchor,
   mixinConstraintValidation,
 } from '../../labs/behaviors/constraint-validation.js';
-import {mixinElementInternals} from '../../labs/behaviors/element-internals.js';
+import {
+  internals,
+  mixinElementInternals,
+} from '../../labs/behaviors/element-internals.js';
 import {
   getFormState,
   getFormValue,
@@ -111,6 +114,12 @@ export class Checkbox extends checkboxBaseClass {
       this.prevDisabled = changed.get('disabled') ?? this.disabled;
       this.prevIndeterminate =
         changed.get('indeterminate') ?? this.indeterminate;
+
+      if (this.checked) {
+        this[internals].states.add('checked');
+      } else {
+        this[internals].states.delete('checked');
+      }
     }
 
     super.update(changed);
diff --git a/checkbox/internal/checkbox_test.ts b/checkbox/internal/checkbox_test.ts
index 61f368a332..dbfe06b843 100644
--- a/checkbox/internal/checkbox_test.ts
+++ b/checkbox/internal/checkbox_test.ts
@@ -50,6 +50,7 @@ describe('checkbox', () => {
       expect(harness.element.indeterminate).toEqual(false);
       expect(harness.element.disabled).toEqual(false);
       expect(harness.element.value).toEqual('on');
+      expect(harness.element.matches(':state(checked)')).toEqual(false);
     });
 
     it('user input updates checked state', async () => {
@@ -57,6 +58,7 @@ describe('checkbox', () => {
       await harness.clickWithMouse();
       await env.waitForStability();
       expect(harness.element.checked).toEqual(true);
+      expect(harness.element.matches(':state(checked)')).toEqual(true);
     });
 
     it('should trigger changed event when checkbox is selected', async () => {
diff --git a/docs/components/checkbox.md b/docs/components/checkbox.md
index 2ae0332224..82ebc97bf5 100644
--- a/docs/components/checkbox.md
+++ b/docs/components/checkbox.md
@@ -209,3 +209,9 @@ Token                                    | Default value
 <!-- mdformat on(autogenerated might break rendering in catalog) -->
 
 <!-- auto-generated API docs end -->
+
+#### States
+
+| State | Description |
+| --- | --- |
+| `checked` | Set if this checkbox is checked. |
diff --git a/package.json b/package.json
index e74c250091..dcf0c8be44 100644
--- a/package.json
+++ b/package.json
@@ -65,6 +65,7 @@
     "@rollup/plugin-node-resolve": "^15.2.3",
     "@rollup/plugin-terser": "^0.4.4",
     "@types/jasmine": "^4.0.3",
+    "@types/web": "^0.0.175",
     "@web/test-runner": "^0.18.2",
     "@web/test-runner-playwright": "^0.9.0",
     "jasmine": "^4.5.0",