diff --git a/src/mount.ts b/src/mount.ts
index 27735767c..4d765ef42 100644
--- a/src/mount.ts
+++ b/src/mount.ts
@@ -516,6 +516,24 @@ export function mount(
     app.mixin(mixin)
   }
 
+  // mixin for initial data of script setup composition components
+  if (options?.data) {
+    const providedData = options.data()
+    const mixin = defineComponent({
+      beforeCreate() {
+        if (hasSetupState(this)) {
+          for (const [k, v] of Object.entries(
+            providedData as { [key: string]: any }
+          )) {
+            this.$.setupState[k] = v
+          }
+        }
+      }
+    })
+
+    app.mixin(mixin)
+  }
+
   // AppConfig
   if (global.config) {
     for (const [k, v] of Object.entries(global.config) as [
diff --git a/src/vueWrapper.ts b/src/vueWrapper.ts
index 1d5fb40a0..8062d5d72 100644
--- a/src/vueWrapper.ts
+++ b/src/vueWrapper.ts
@@ -242,10 +242,16 @@ export class VueWrapper<
   }
 
   setData(data: Record<string, unknown>): Promise<void> {
-    mergeDeep(this.componentVM.$data, data)
+    //this.componentVM.$data is not defined on all composition api components
+    //script setup components store data in root node instead of $data
+    if (hasSetupState(this.vm)) {
+      const target = this.componentVM as Record<string, unknown>
+      mergeDeep(target, data)
+    } else {
+      mergeDeep(this.componentVM.$data, data)
+    }
     return nextTick()
   }
-
   setProps(props: Record<string, unknown>): Promise<void> {
     // if this VM's parent is not the root or if setProps does not exist, error out
     if (this.vm.$parent !== this.rootVM || !this.__setProps) {
diff --git a/tests/components/SimpleData.vue b/tests/components/SimpleData.vue
new file mode 100644
index 000000000..be5d801fd
--- /dev/null
+++ b/tests/components/SimpleData.vue
@@ -0,0 +1,13 @@
+<template>
+  <div>sArray:{{dataStringArray}}|s:{{dataString}}</div>
+</template>
+
+
+<script setup lang="ts">
+
+import {ref} from "vue";
+
+const dataStringArray = ref<string[]>(['initialA','initialB'])
+const dataString = ref<string>('initialC')
+
+</script>
diff --git a/tests/components/SimpleDataClassComponent.vue b/tests/components/SimpleDataClassComponent.vue
new file mode 100644
index 000000000..71c8d3ec6
--- /dev/null
+++ b/tests/components/SimpleDataClassComponent.vue
@@ -0,0 +1,16 @@
+<template>
+  <div>sArray:{{dataStringArray}}|s:{{dataString}}</div>
+</template>
+
+<script lang="ts">
+import { Options, Vue } from 'vue-class-component'
+
+@Options({})
+export default class SimpleDataClassComponent extends Vue {
+  dataText: string = ''
+  msg!: string // declared for type-checking
+
+  dataStringArray : string[]= ['initialA','initialB']
+  dataString: string  = 'initialC'
+}
+</script>
diff --git a/tests/mount.spec.ts b/tests/mount.spec.ts
index 7c77d66c4..77037f55d 100644
--- a/tests/mount.spec.ts
+++ b/tests/mount.spec.ts
@@ -2,6 +2,8 @@ import { describe, expect, it, vi } from 'vitest'
 import { defineComponent } from 'vue'
 import { mount } from '../src'
 import HelloFromVitestPlayground from './components/HelloFromVitestPlayground.vue'
+import SimpleData from './components/SimpleData.vue'
+import SimpleDataClassComponent from './components/SimpleDataClassComponent.vue'
 
 describe('mount: general tests', () => {
   it('correctly handles component, throwing on mount', () => {
@@ -32,4 +34,55 @@ describe('mount: general tests', () => {
 
     expect(spy).not.toHaveBeenCalled()
   })
+
+  it('should respect a data callback when using mount/shallowmount on ClassComponent api component', async () => {
+    const wrapper = mount(SimpleDataClassComponent, {
+      data: () => {
+        return {
+          dataStringArray: ['setA', 'setB'],
+          dataString: 'setC'
+        }
+      }
+    })
+    expect(wrapper.html()).toEqual(
+      '<div>sArray:[\n  "setA",\n  "setB"\n  ]|s:setC</div>'
+    )
+  })
+
+  it('should respect a data callback when using mount/shallowmount on composition api component', async () => {
+    const wrapper = mount(SimpleData, {
+      data: () => {
+        return {
+          dataStringArray: ['setA', 'setB'],
+          dataString: 'setC'
+        }
+      }
+    })
+    expect(wrapper.html()).toEqual(
+      '<div>sArray:[\n  "setA",\n  "setB"\n  ]|s:setC</div>'
+    )
+  })
+
+  it('should respect a data callback when using mount/shallowmount on inline component', async () => {
+    const Component = {
+      template: `<div>sArray:{{dataStringArray}}|s:{{dataString}}</div>`,
+      data: () => ({
+        dataStringArray: ['initialA', 'initialB'],
+        dataString: 'initialC'
+      })
+    }
+
+    const wrapper = mount(Component, {
+      data: () => {
+        return {
+          dataStringArray: ['setA', 'setB'],
+          dataString: 'setC'
+        }
+      }
+    })
+
+    expect(wrapper.html()).toEqual(
+      '<div>sArray:[\n  "setA",\n  "setB"\n  ]|s:setC</div>'
+    )
+  })
 })
diff --git a/tests/setData.spec.ts b/tests/setData.spec.ts
index 30cfabd55..e00106bb5 100644
--- a/tests/setData.spec.ts
+++ b/tests/setData.spec.ts
@@ -1,7 +1,8 @@
 import { describe, expect, it, vi } from 'vitest'
-import { defineComponent, ref } from 'vue'
-
+import { defineComponent } from 'vue'
 import { mount } from '../src'
+import SimpleData from './components/SimpleData.vue'
+import SimpleDataClassComponent from './components/SimpleDataClassComponent.vue'
 
 describe('setData', () => {
   it('sets component data', async () => {
@@ -111,20 +112,6 @@ describe('setData', () => {
     )
   })
 
-  it('does not modify composition API setup data', async () => {
-    const Component = defineComponent({
-      template: `<div>Count is: {{ count }}</div>`,
-      setup: () => ({ count: ref(1) })
-    })
-    const wrapper = mount(Component)
-
-    expect(wrapper.html()).toContain('Count is: 1')
-
-    expect(() => wrapper.setData({ count: 2 })).toThrowError(
-      'Cannot add property count'
-    )
-  })
-
   // https://github.com/vuejs/test-utils/issues/538
   it('updates data set via data mounting option using setData', async () => {
     const Comp = defineComponent<
@@ -214,4 +201,58 @@ describe('setData', () => {
     expect(wrapper.vm.value).toBeInstanceOf(Date)
     expect(wrapper.vm.value!.toISOString()).toBe('2022-08-11T12:15:54.000Z')
   })
+
+  it('should handle setData on ClassComponent api component', async () => {
+    const wrapper = mount(SimpleDataClassComponent)
+    expect(wrapper.html()).toEqual(
+      '<div>sArray:[\n  "initialA",\n  "initialB"\n  ]|s:initialC</div>'
+    )
+
+    await wrapper.setData({
+      dataStringArray: ['setA', 'setB'],
+      dataString: 'setC'
+    })
+
+    expect(wrapper.html()).toEqual(
+      '<div>sArray:[\n  "setA",\n  "setB"\n  ]|s:setC</div>'
+    )
+  })
+
+  it('should handle setData on composition api component', async () => {
+    const wrapper = mount(SimpleData)
+    expect(wrapper.html()).toEqual(
+      '<div>sArray:[\n  "initialA",\n  "initialB"\n  ]|s:initialC</div>'
+    )
+
+    await wrapper.setData({
+      dataStringArray: ['setA', 'setB'],
+      dataString: 'setC'
+    })
+
+    expect(wrapper.html()).toEqual(
+      '<div>sArray:[\n  "setA",\n  "setB"\n  ]|s:setC</div>'
+    )
+  })
+
+  it('should handle setData on inline component component', async () => {
+    const Component = {
+      template: `<div>sArray:{{dataStringArray}}|s:{{dataString}}</div>`,
+      data: () => ({
+        dataStringArray: ['initialA', 'initialB'],
+        dataString: 'initialC'
+      })
+    }
+    const wrapper = mount(Component, {
+      data: () => {
+        return {
+          dataStringArray: ['setA', 'setB'],
+          dataString: 'setC'
+        }
+      }
+    })
+
+    expect(wrapper.html()).toEqual(
+      '<div>sArray:[\n  "setA",\n  "setB"\n  ]|s:setC</div>'
+    )
+  })
 })