diff --git a/packages/react-reconciler/src/ReactFiberCommitWork.new.js b/packages/react-reconciler/src/ReactFiberCommitWork.new.js
index 84a20638ef299..fb4c942ab6eea 100644
--- a/packages/react-reconciler/src/ReactFiberCommitWork.new.js
+++ b/packages/react-reconciler/src/ReactFiberCommitWork.new.js
@@ -67,9 +67,15 @@ import {
   Placement,
   Snapshot,
   Update,
+  Passive,
+  PassiveMask,
 } from './ReactFiberFlags';
 import getComponentName from 'shared/getComponentName';
 import invariant from 'shared/invariant';
+import {
+  resetCurrentFiber as resetCurrentDebugFiberInDEV,
+  setCurrentFiber as setCurrentDebugFiberInDEV,
+} from './ReactCurrentFiber';
 
 import {onCommitUnmount} from './ReactFiberDevToolsHook.new';
 import {resolveDefaultProps} from './ReactFiberLazyComponent.new';
@@ -78,6 +84,8 @@ import {
   getCommitTime,
   recordLayoutEffectDuration,
   startLayoutEffectTimer,
+  recordPassiveEffectDuration,
+  startPassiveEffectTimer,
 } from './ReactProfilerTimer.new';
 import {ProfileMode} from './ReactTypeOfMode';
 import {commitUpdateQueue} from './ReactUpdateQueue.new';
@@ -134,6 +142,8 @@ if (__DEV__) {
 
 const PossiblyWeakSet = typeof WeakSet === 'function' ? WeakSet : Set;
 
+let nextEffect: Fiber | null = null;
+
 const callComponentWillUnmountWithTimer = function(current, instance) {
   instance.props = current.memoizedProps;
   instance.state = current.memoizedState;
@@ -1798,6 +1808,117 @@ function commitResetTextContent(current: Fiber) {
   resetTextContent(current.stateNode);
 }
 
+export function commitPassiveMountEffects(
+  root: FiberRoot,
+  firstChild: Fiber,
+): void {
+  nextEffect = firstChild;
+  commitPassiveMountEffects_begin(firstChild, root);
+}
+
+function commitPassiveMountEffects_begin(subtreeRoot: Fiber, root: FiberRoot) {
+  while (nextEffect !== null) {
+    const fiber = nextEffect;
+    const firstChild = fiber.child;
+    if ((fiber.subtreeFlags & PassiveMask) !== NoFlags && firstChild !== null) {
+      ensureCorrectReturnPointer(firstChild, fiber);
+      nextEffect = firstChild;
+    } else {
+      commitPassiveMountEffects_complete(subtreeRoot, root);
+    }
+  }
+}
+
+function commitPassiveMountEffects_complete(
+  subtreeRoot: Fiber,
+  root: FiberRoot,
+) {
+  while (nextEffect !== null) {
+    const fiber = nextEffect;
+    if ((fiber.flags & Passive) !== NoFlags) {
+      if (__DEV__) {
+        setCurrentDebugFiberInDEV(fiber);
+        invokeGuardedCallback(
+          null,
+          commitPassiveMountOnFiber,
+          null,
+          root,
+          fiber,
+        );
+        if (hasCaughtError()) {
+          const error = clearCaughtError();
+          captureCommitPhaseError(fiber, error);
+        }
+        resetCurrentDebugFiberInDEV();
+      } else {
+        try {
+          commitPassiveMountOnFiber(root, fiber);
+        } catch (error) {
+          captureCommitPhaseError(fiber, error);
+        }
+      }
+    }
+
+    if (fiber === subtreeRoot) {
+      nextEffect = null;
+      return;
+    }
+
+    const sibling = fiber.sibling;
+    if (sibling !== null) {
+      ensureCorrectReturnPointer(sibling, fiber.return);
+      nextEffect = sibling;
+      return;
+    }
+
+    nextEffect = fiber.return;
+  }
+}
+
+function commitPassiveMountOnFiber(
+  finishedRoot: FiberRoot,
+  finishedWork: Fiber,
+): void {
+  switch (finishedWork.tag) {
+    case FunctionComponent:
+    case ForwardRef:
+    case SimpleMemoComponent: {
+      if (
+        enableProfilerTimer &&
+        enableProfilerCommitHooks &&
+        finishedWork.mode & ProfileMode
+      ) {
+        startPassiveEffectTimer();
+        try {
+          commitHookEffectListMount(HookPassive | HookHasEffect, finishedWork);
+        } finally {
+          recordPassiveEffectDuration(finishedWork);
+        }
+      } else {
+        commitHookEffectListMount(HookPassive | HookHasEffect, finishedWork);
+      }
+      break;
+    }
+  }
+}
+
+let didWarnWrongReturnPointer = false;
+function ensureCorrectReturnPointer(fiber, expectedReturnFiber) {
+  if (__DEV__) {
+    if (!didWarnWrongReturnPointer && fiber.return !== expectedReturnFiber) {
+      didWarnWrongReturnPointer = true;
+      console.error(
+        'Internal React error: Return pointer is inconsistent ' +
+          'with parent.',
+      );
+    }
+  }
+
+  // TODO: Remove this assignment once we're confident that it won't break
+  // anything, by checking the warning logs for the above invariant
+  fiber.return = expectedReturnFiber;
+}
+
 export {
   commitBeforeMutationLifeCycles,
   commitResetTextContent,
diff --git a/packages/react-reconciler/src/ReactFiberCommitWork.old.js b/packages/react-reconciler/src/ReactFiberCommitWork.old.js
index 94d137c99bdc2..7f98172a30edb 100644
--- a/packages/react-reconciler/src/ReactFiberCommitWork.old.js
+++ b/packages/react-reconciler/src/ReactFiberCommitWork.old.js
@@ -67,9 +67,15 @@ import {
   Placement,
   Snapshot,
   Update,
+  Passive,
+  PassiveMask,
 } from './ReactFiberFlags';
 import getComponentName from 'shared/getComponentName';
 import invariant from 'shared/invariant';
+import {
+  resetCurrentFiber as resetCurrentDebugFiberInDEV,
+  setCurrentFiber as setCurrentDebugFiberInDEV,
+} from './ReactCurrentFiber';
 
 import {onCommitUnmount} from './ReactFiberDevToolsHook.old';
 import {resolveDefaultProps} from './ReactFiberLazyComponent.old';
@@ -78,6 +84,8 @@ import {
   getCommitTime,
   recordLayoutEffectDuration,
   startLayoutEffectTimer,
+  recordPassiveEffectDuration,
+  startPassiveEffectTimer,
 } from './ReactProfilerTimer.old';
 import {ProfileMode} from './ReactTypeOfMode';
 import {commitUpdateQueue} from './ReactUpdateQueue.old';
@@ -134,6 +142,8 @@ if (__DEV__) {
 
 const PossiblyWeakSet = typeof WeakSet === 'function' ? WeakSet : Set;
 
+let nextEffect: Fiber | null = null;
+
 const callComponentWillUnmountWithTimer = function(current, instance) {
   instance.props = current.memoizedProps;
   instance.state = current.memoizedState;
@@ -1798,6 +1808,117 @@ function commitResetTextContent(current: Fiber) {
   resetTextContent(current.stateNode);
 }
 
+export function commitPassiveMountEffects(
+  root: FiberRoot,
+  firstChild: Fiber,
+): void {
+  nextEffect = firstChild;
+  commitPassiveMountEffects_begin(firstChild, root);
+}
+
+function commitPassiveMountEffects_begin(subtreeRoot: Fiber, root: FiberRoot) {
+  while (nextEffect !== null) {
+    const fiber = nextEffect;
+    const firstChild = fiber.child;
+    if ((fiber.subtreeFlags & PassiveMask) !== NoFlags && firstChild !== null) {
+      ensureCorrectReturnPointer(firstChild, fiber);
+      nextEffect = firstChild;
+    } else {
+      commitPassiveMountEffects_complete(subtreeRoot, root);
+    }
+  }
+}
+
+function commitPassiveMountEffects_complete(
+  subtreeRoot: Fiber,
+  root: FiberRoot,
+) {
+  while (nextEffect !== null) {
+    const fiber = nextEffect;
+    if ((fiber.flags & Passive) !== NoFlags) {
+      if (__DEV__) {
+        setCurrentDebugFiberInDEV(fiber);
+        invokeGuardedCallback(
+          null,
+          commitPassiveMountOnFiber,
+          null,
+          root,
+          fiber,
+        );
+        if (hasCaughtError()) {
+          const error = clearCaughtError();
+          captureCommitPhaseError(fiber, error);
+        }
+        resetCurrentDebugFiberInDEV();
+      } else {
+        try {
+          commitPassiveMountOnFiber(root, fiber);
+        } catch (error) {
+          captureCommitPhaseError(fiber, error);
+        }
+      }
+    }
+
+    if (fiber === subtreeRoot) {
+      nextEffect = null;
+      return;
+    }
+
+    const sibling = fiber.sibling;
+    if (sibling !== null) {
+      ensureCorrectReturnPointer(sibling, fiber.return);
+      nextEffect = sibling;
+      return;
+    }
+
+    nextEffect = fiber.return;
+  }
+}
+
+function commitPassiveMountOnFiber(
+  finishedRoot: FiberRoot,
+  finishedWork: Fiber,
+): void {
+  switch (finishedWork.tag) {
+    case FunctionComponent:
+    case ForwardRef:
+    case SimpleMemoComponent: {
+      if (
+        enableProfilerTimer &&
+        enableProfilerCommitHooks &&
+        finishedWork.mode & ProfileMode
+      ) {
+        startPassiveEffectTimer();
+        try {
+          commitHookEffectListMount(HookPassive | HookHasEffect, finishedWork);
+        } finally {
+          recordPassiveEffectDuration(finishedWork);
+        }
+      } else {
+        commitHookEffectListMount(HookPassive | HookHasEffect, finishedWork);
+      }
+      break;
+    }
+  }
+}
+
+let didWarnWrongReturnPointer = false;
+function ensureCorrectReturnPointer(fiber, expectedReturnFiber) {
+  if (__DEV__) {
+    if (!didWarnWrongReturnPointer && fiber.return !== expectedReturnFiber) {
+      didWarnWrongReturnPointer = true;
+      console.error(
+        'Internal React error: Return pointer is inconsistent ' +
+          'with parent.',
+      );
+    }
+  }
+
+  // TODO: Remove this assignment once we're confident that it won't break
+  // anything, by checking the warning logs for the above invariant
+  fiber.return = expectedReturnFiber;
+}
+
 export {
   commitBeforeMutationLifeCycles,
   commitResetTextContent,
diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.new.js b/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
index 042361ebdb1b3..3177abb63c511 100644
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
@@ -193,6 +193,7 @@ import {
   commitPassiveEffectDurations,
   commitResetTextContent,
   isSuspenseBoundaryBeingHidden,
+  commitPassiveMountEffects,
 } from './ReactFiberCommitWork.new';
 import {enqueueUpdate} from './ReactUpdateQueue.new';
 import {resetContextDependencies} from './ReactFiberNewContext.new';
@@ -339,7 +340,6 @@ let rootDoesHavePassiveEffects: boolean = false;
 let rootWithPendingPassiveEffects: FiberRoot | null = null;
 let pendingPassiveEffectsRenderPriority: ReactPriorityLevel = NoSchedulerPriority;
 let pendingPassiveEffectsLanes: Lanes = NoLanes;
-let pendingPassiveHookEffectsMount: Array<HookEffect | Fiber> = [];
 let pendingPassiveHookEffectsUnmount: Array<HookEffect | Fiber> = [];
 let pendingPassiveProfilerEffects: Array<Fiber> = [];
 
@@ -2489,7 +2489,6 @@ export function enqueuePendingPassiveHookEffectMount(
   fiber: Fiber,
   effect: HookEffect,
 ): void {
-  pendingPassiveHookEffectsMount.push(effect, fiber);
   if (!rootDoesHavePassiveEffects) {
     rootDoesHavePassiveEffects = true;
     scheduleCallback(NormalSchedulerPriority, () => {
@@ -2520,11 +2519,6 @@ export function enqueuePendingPassiveHookEffectUnmount(
   }
 }
 
-function invokePassiveEffectCreate(effect: HookEffect): void {
-  const create = effect.create;
-  effect.destroy = create();
-}
-
 function flushPassiveEffectsImpl() {
   if (rootWithPendingPassiveEffects === null) {
     return false;
@@ -2626,68 +2620,9 @@ function flushPassiveEffectsImpl() {
     }
   }
   // Second pass: Create new passive effects.
-  const mountEffects = pendingPassiveHookEffectsMount;
-  pendingPassiveHookEffectsMount = [];
-  for (let i = 0; i < mountEffects.length; i += 2) {
-    const effect = ((mountEffects[i]: any): HookEffect);
-    const fiber = ((mountEffects[i + 1]: any): Fiber);
-    if (__DEV__) {
-      setCurrentDebugFiberInDEV(fiber);
-      if (
-        enableProfilerTimer &&
-        enableProfilerCommitHooks &&
-        fiber.mode & ProfileMode
-      ) {
-        startPassiveEffectTimer();
-        invokeGuardedCallback(null, invokePassiveEffectCreate, null, effect);
-        recordPassiveEffectDuration(fiber);
-      } else {
-        invokeGuardedCallback(null, invokePassiveEffectCreate, null, effect);
-      }
-      if (hasCaughtError()) {
-        invariant(fiber !== null, 'Should be working on an effect.');
-        const error = clearCaughtError();
-        captureCommitPhaseError(fiber, error);
-      }
-      resetCurrentDebugFiberInDEV();
-    } else {
-      try {
-        const create = effect.create;
-        if (
-          enableProfilerTimer &&
-          enableProfilerCommitHooks &&
-          fiber.mode & ProfileMode
-        ) {
-          try {
-            startPassiveEffectTimer();
-            effect.destroy = create();
-          } finally {
-            recordPassiveEffectDuration(fiber);
-          }
-        } else {
-          effect.destroy = create();
-        }
-      } catch (error) {
-        invariant(fiber !== null, 'Should be working on an effect.');
-        captureCommitPhaseError(fiber, error);
-      }
-    }
-  }
-
-  // Note: This currently assumes there are no passive effects on the root fiber
-  // because the root is not part of its own effect list.
-  // This could change in the future.
-  let effect = root.current.firstEffect;
-  while (effect !== null) {
-    const nextNextEffect = effect.nextEffect;
-    // Remove nextEffect pointer to assist GC
-    effect.nextEffect = null;
-    if (effect.flags & Deletion) {
-      detachFiberAfterEffects(effect);
-    }
-    effect = nextNextEffect;
-  }
+  commitPassiveMountEffects(root, root.current);
 
+  // TODO: Move to commitPassiveMountEffects
   if (enableProfilerTimer && enableProfilerCommitHooks) {
     const profilerEffects = pendingPassiveProfilerEffects;
     pendingPassiveProfilerEffects = [];
diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.old.js b/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
index 65157db61925d..dc21ff6b7f3ed 100644
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
@@ -193,6 +193,7 @@ import {
   commitPassiveEffectDurations,
   commitResetTextContent,
   isSuspenseBoundaryBeingHidden,
+  commitPassiveMountEffects,
 } from './ReactFiberCommitWork.old';
 import {enqueueUpdate} from './ReactUpdateQueue.old';
 import {resetContextDependencies} from './ReactFiberNewContext.old';
@@ -339,7 +340,6 @@ let rootDoesHavePassiveEffects: boolean = false;
 let rootWithPendingPassiveEffects: FiberRoot | null = null;
 let pendingPassiveEffectsRenderPriority: ReactPriorityLevel = NoSchedulerPriority;
 let pendingPassiveEffectsLanes: Lanes = NoLanes;
-let pendingPassiveHookEffectsMount: Array<HookEffect | Fiber> = [];
 let pendingPassiveHookEffectsUnmount: Array<HookEffect | Fiber> = [];
 let pendingPassiveProfilerEffects: Array<Fiber> = [];
 
@@ -2489,7 +2489,6 @@ export function enqueuePendingPassiveHookEffectMount(
   fiber: Fiber,
   effect: HookEffect,
 ): void {
-  pendingPassiveHookEffectsMount.push(effect, fiber);
   if (!rootDoesHavePassiveEffects) {
     rootDoesHavePassiveEffects = true;
     scheduleCallback(NormalSchedulerPriority, () => {
@@ -2520,11 +2519,6 @@ export function enqueuePendingPassiveHookEffectUnmount(
   }
 }
 
-function invokePassiveEffectCreate(effect: HookEffect): void {
-  const create = effect.create;
-  effect.destroy = create();
-}
-
 function flushPassiveEffectsImpl() {
   if (rootWithPendingPassiveEffects === null) {
     return false;
@@ -2626,68 +2620,9 @@ function flushPassiveEffectsImpl() {
     }
   }
   // Second pass: Create new passive effects.
-  const mountEffects = pendingPassiveHookEffectsMount;
-  pendingPassiveHookEffectsMount = [];
-  for (let i = 0; i < mountEffects.length; i += 2) {
-    const effect = ((mountEffects[i]: any): HookEffect);
-    const fiber = ((mountEffects[i + 1]: any): Fiber);
-    if (__DEV__) {
-      setCurrentDebugFiberInDEV(fiber);
-      if (
-        enableProfilerTimer &&
-        enableProfilerCommitHooks &&
-        fiber.mode & ProfileMode
-      ) {
-        startPassiveEffectTimer();
-        invokeGuardedCallback(null, invokePassiveEffectCreate, null, effect);
-        recordPassiveEffectDuration(fiber);
-      } else {
-        invokeGuardedCallback(null, invokePassiveEffectCreate, null, effect);
-      }
-      if (hasCaughtError()) {
-        invariant(fiber !== null, 'Should be working on an effect.');
-        const error = clearCaughtError();
-        captureCommitPhaseError(fiber, error);
-      }
-      resetCurrentDebugFiberInDEV();
-    } else {
-      try {
-        const create = effect.create;
-        if (
-          enableProfilerTimer &&
-          enableProfilerCommitHooks &&
-          fiber.mode & ProfileMode
-        ) {
-          try {
-            startPassiveEffectTimer();
-            effect.destroy = create();
-          } finally {
-            recordPassiveEffectDuration(fiber);
-          }
-        } else {
-          effect.destroy = create();
-        }
-      } catch (error) {
-        invariant(fiber !== null, 'Should be working on an effect.');
-        captureCommitPhaseError(fiber, error);
-      }
-    }
-  }
-
-  // Note: This currently assumes there are no passive effects on the root fiber
-  // because the root is not part of its own effect list.
-  // This could change in the future.
-  let effect = root.current.firstEffect;
-  while (effect !== null) {
-    const nextNextEffect = effect.nextEffect;
-    // Remove nextEffect pointer to assist GC
-    effect.nextEffect = null;
-    if (effect.flags & Deletion) {
-      detachFiberAfterEffects(effect);
-    }
-    effect = nextNextEffect;
-  }
+  commitPassiveMountEffects(root, root.current);
 
+  // TODO: Move to commitPassiveMountEffects
   if (enableProfilerTimer && enableProfilerCommitHooks) {
     const profilerEffects = pendingPassiveProfilerEffects;
     pendingPassiveProfilerEffects = [];