diff --git a/src/vanilla/store.ts b/src/vanilla/store.ts
index c7390cb45d..457a64b245 100644
--- a/src/vanilla/store.ts
+++ b/src/vanilla/store.ts
@@ -595,7 +595,14 @@ const buildStore = (getAtomState: StoreArgs[0]): Store => {
               return result
             })
             if (onUnmount) {
-              mounted.u = onUnmount
+              mounted.u = () => {
+                isSync = true
+                try {
+                  onUnmount()
+                } finally {
+                  isSync = false
+                }
+              }
             }
           } finally {
             isSync = false
diff --git a/tests/vanilla/store.test.tsx b/tests/vanilla/store.test.tsx
index c0be322c45..92401f2431 100644
--- a/tests/vanilla/store.test.tsx
+++ b/tests/vanilla/store.test.tsx
@@ -579,3 +579,86 @@ it('should update derived atom even if dependances changed (#2697)', () => {
   store.set(primitiveAtom, 1)
   expect(onChangeDerived).toHaveBeenCalledTimes(1)
 })
+
+describe('should invoke flushPending only after all atoms are updated (#2804)', () => {
+  const store = createStore()
+  it('should invoke flushPending only after all atoms are updated with set', () => {
+    const a = atom(0)
+    const setResult = []
+    const w = atom(null, (_get, set, value: number) => {
+      setResult.push('before set')
+      set(a, value)
+      setResult.push('after set')
+    })
+    store.sub(a, () => {
+      setResult.push('a value changed - ' + store.get(a))
+    })
+    setResult.push('before store.set')
+    store.set(w, 1)
+    setResult.push('after store.set')
+    expect(setResult).not.toEqual([
+      'before store.set',
+      'before set',
+      'a value changed - 1',
+      'after set',
+      'after store.set',
+    ])
+    expect(setResult).toEqual([
+      'before store.set',
+      'before set',
+      'after set',
+      'a value changed - 1',
+      'after store.set',
+    ])
+  })
+  it('should invoke flushPending only after all atoms are updated with mount', () => {
+    const mountResult = []
+    const a = atom(0)
+    const m = atom(null, (_get, set, value: number) => {
+      set(a, value)
+    })
+    m.onMount = (setSelf) => {
+      mountResult.push('before onMount setSelf')
+      setSelf(1)
+      mountResult.push('after onMount setSelf')
+      return () => {
+        mountResult.push('before onUnmount setSelf')
+        setSelf(2)
+        mountResult.push('after onUnmount setSelf')
+      }
+    }
+    mountResult.push('before store.sub')
+    store.sub(a, () => {
+      mountResult.push('a value changed - ' + store.get(a))
+    })
+    const unsub = store.sub(m, () => {})
+    mountResult.push('after store.sub')
+    mountResult.push('before store.unsub')
+    unsub()
+    mountResult.push('after store.unsub')
+    expect(mountResult).not.toEqual([
+      'before store.sub',
+      'before onMount setSelf',
+      'a value changed - 1',
+      'after onMount setSelf',
+      'after store.sub',
+      'before store.unsub',
+      'before onUnmount setSelf',
+      'a value changed - 2',
+      'after onUnmount setSelf',
+      'after store.unsub',
+    ])
+    expect(mountResult).toEqual([
+      'before store.sub',
+      'before onMount setSelf',
+      'after onMount setSelf',
+      'a value changed - 1',
+      'after store.sub',
+      'before store.unsub',
+      'before onUnmount setSelf',
+      'after onUnmount setSelf',
+      'a value changed - 2',
+      'after store.unsub',
+    ])
+  })
+})