diff --git a/packages/reactivity/__tests__/reactive.spec.ts b/packages/reactivity/__tests__/reactive.spec.ts
index ed7097aeb67..eb6ad1ac862 100644
--- a/packages/reactivity/__tests__/reactive.spec.ts
+++ b/packages/reactivity/__tests__/reactive.spec.ts
@@ -307,6 +307,26 @@ describe('reactivity/reactive', () => {
     expect(() => markRaw(obj)).not.toThrowError()
   })
 
+  test('markRaw preserves opt-out on non-extensible targets', () => {
+    const sealed = Object.seal({ a: 1 })
+    const marked = markRaw(sealed)
+    expect(marked).toBe(sealed)
+    // SKIP flag cannot be added onto a sealed target, so reactive() learns
+    // about the opt-out via the side rawSet instead.
+    expect(reactive(marked)).toBe(sealed)
+    expect(isReactive(reactive({ inner: markRaw(sealed) }).inner)).toBe(false)
+  })
+
+  test('deep traverse should skip markRaw non-extensible targets', async () => {
+    const { traverse } = await import('../src/watch')
+    const sealed = Object.seal({ inner: { a: 1 } })
+    const marked = markRaw(sealed)
+    const seen = new Map()
+    traverse(marked, Infinity, seen)
+    // SKIP-flag markRaw stops here; the rawSet fallback must do the same.
+    expect(seen.has(marked.inner)).toBe(false)
+  })
+
   test('markRaw should not redefine on an marked object', () => {
     const obj = markRaw({ foo: 1 })
     const raw = markRaw(obj)
@@ -321,16 +341,34 @@ describe('reactivity/reactive', () => {
     expect(b.a === a).toBe(false)
   })
 
-  test('should not observe non-extensible objects', () => {
+  test('should not observe frozen objects', () => {
     const obj = reactive({
-      foo: Object.preventExtensions({ a: 1 }),
-      // sealed or frozen objects are considered non-extensible as well
-      bar: Object.freeze({ a: 1 }),
-      baz: Object.seal({ a: 1 }),
+      foo: Object.freeze({ a: 1 }),
     })
     expect(isReactive(obj.foo)).toBe(false)
-    expect(isReactive(obj.bar)).toBe(false)
-    expect(isReactive(obj.baz)).toBe(false)
+  })
+
+  test('should observe sealed and non-extensible objects', () => {
+    // sealed and Object.preventExtensions targets still allow mutating their
+    // existing keys, so reactive() should proxy them. See issue #14893.
+    const sealed = reactive(Object.seal({ a: 1 }))
+    const nonExtensible = reactive(Object.preventExtensions({ a: 1 }))
+    expect(isReactive(sealed)).toBe(true)
+    expect(isReactive(nonExtensible)).toBe(true)
+
+    let dummy
+    effect(() => {
+      dummy = sealed.a + nonExtensible.a
+    })
+    expect(dummy).toBe(2)
+    sealed.a = 10
+    nonExtensible.a = 20
+    expect(dummy).toBe(30)
+
+    // siblings share the same createReactiveObject guard.
+    expect(isReactive(shallowReactive(Object.seal({ a: 1 })))).toBe(true)
+    expect(isReadonly(readonly(Object.seal({ a: 1 })))).toBe(true)
+    expect(isReadonly(shallowReadonly(Object.seal({ a: 1 })))).toBe(true)
   })
 
   test('should not observe objects with __v_skip', () => {
diff --git a/packages/reactivity/src/reactive.ts b/packages/reactivity/src/reactive.ts
index 3075f47a5ff..6c375cff9a6 100644
--- a/packages/reactivity/src/reactive.ts
+++ b/packages/reactivity/src/reactive.ts
@@ -23,6 +23,20 @@ export interface Target {
   [ReactiveFlags.RAW]?: any
 }
 
+// non-extensible targets opted out via markRaw (SKIP flag can't be defined on them)
+const rawSet: WeakSet<object> = new WeakSet<object>()
+
+/**
+ * Internal: true if the value has opted out of reactivity via markRaw,
+ * either through the SKIP flag or through the rawSet fallback.
+ */
+export function isRawMarked(value: unknown): boolean {
+  return (
+    !!value &&
+    (!!(value as Target)[ReactiveFlags.SKIP] || rawSet.has(value as object))
+  )
+}
+
 export const reactiveMap: WeakMap<Target, any> = new WeakMap<Target, any>()
 export const shallowReactiveMap: WeakMap<Target, any> = new WeakMap<
   Target,
@@ -284,8 +298,8 @@ function createReactiveObject(
   ) {
     return target
   }
-  // only specific value types can be observed.
-  if (target[ReactiveFlags.SKIP] || !Object.isExtensible(target)) {
+  // skip frozen targets and anything opted out via markRaw.
+  if (isRawMarked(target) || Object.isFrozen(target)) {
     return target
   }
   // target already has corresponding Proxy
@@ -418,8 +432,13 @@ export type Raw<T> = T & { [RawSymbol]?: true }
  * @see {@link https://vuejs.org/api/reactivity-advanced.html#markraw}
  */
 export function markRaw<T extends object>(value: T): Raw<T> {
-  if (!hasOwn(value, ReactiveFlags.SKIP) && Object.isExtensible(value)) {
-    def(value, ReactiveFlags.SKIP, true)
+  if (!hasOwn(value, ReactiveFlags.SKIP)) {
+    if (Object.isExtensible(value)) {
+      def(value, ReactiveFlags.SKIP, true)
+    } else {
+      // SKIP can't be defined on a non-extensible target; track it via rawSet.
+      rawSet.add(value)
+    }
   }
   return value
 }
diff --git a/packages/reactivity/src/watch.ts b/packages/reactivity/src/watch.ts
index 6bc009985e0..4717af5b3e2 100644
--- a/packages/reactivity/src/watch.ts
+++ b/packages/reactivity/src/watch.ts
@@ -12,7 +12,7 @@ import {
 } from '@vue/shared'
 import { warn } from './warning'
 import type { ComputedRef } from './computed'
-import { ReactiveFlags } from './constants'
+import { isRawMarked } from './reactive'
 import {
   type DebuggerOptions,
   EffectFlags,
@@ -333,7 +333,7 @@ export function traverse(
   depth: number = Infinity,
   seen?: Map<unknown, number>,
 ): unknown {
-  if (depth <= 0 || !isObject(value) || (value as any)[ReactiveFlags.SKIP]) {
+  if (depth <= 0 || !isObject(value) || isRawMarked(value)) {
     return value
   }