diff --git a/ios/ExpoNotifications/Notifications/NotificationCenterManager.swift b/ios/ExpoNotifications/Notifications/NotificationCenterManager.swift
--- a/ios/ExpoNotifications/Notifications/NotificationCenterManager.swift
+++ b/ios/ExpoNotifications/Notifications/NotificationCenterManager.swift
@@ -42,8 +42,10 @@
   @objc
   public static let shared = NotificationCenterManager()
 
-  var delegates: [NotificationDelegate] = []
-  var pendingResponses: [UNNotificationResponse] = []
+  // Module creation and destruction can overlap across React runtimes.
+  private let stateLock = NSLock()
+  private var delegates: [NotificationDelegate] = []
+  private var pendingResponses: [UNNotificationResponse] = []
   let userNotificationCenter: UNUserNotificationCenter = UNUserNotificationCenter.current()
 
   private override init() {
@@ -62,32 +64,49 @@
   }
 
   public func addDelegate(_ delegate: NotificationDelegate) {
-    delegates.append(delegate)
+    let responses = stateLock.withLock {
+      delegates.append(delegate)
+      return pendingResponses
+    }
     var handled = false
-    for pendingResponse in pendingResponses {
+    for pendingResponse in responses {
       handled = delegate.didReceive(pendingResponse, completionHandler: {}) || handled
     }
     if handled {
-      pendingResponses.removeAll()
+      removePendingResponses(responses)
     }
   }
 
   public func removeDelegate(_ delegate: AnyObject) {
-    if let index = delegates.firstIndex(where: { $0 === delegate }) {
-      delegates.remove(at: index)
+    stateLock.withLock {
+      if let index = delegates.firstIndex(where: { $0 === delegate }) {
+        delegates.remove(at: index)
+      }
+    }
+  }
+
+  private func snapshotDelegates() -> [NotificationDelegate] {
+    stateLock.withLock { delegates }
+  }
+
+  private func removePendingResponses(_ responses: [UNNotificationResponse]) {
+    let identifiers = Set(responses.map(ObjectIdentifier.init))
+    stateLock.withLock {
+      // Keep responses received while delegate callbacks were running.
+      pendingResponses.removeAll { identifiers.contains(ObjectIdentifier($0)) }
     }
   }
 
   // MARK: - Called by PushTokenAppDelegateSubscriber
 
   public func didFailRegistration(_ error: any Error) {
-    for delegate in delegates {
+    for delegate in snapshotDelegates() {
       delegate.didFailRegistration(error)
     }
   }
 
   public func didRegister(_ deviceToken: String) {
-    for delegate in delegates {
+    for delegate in snapshotDelegates() {
       delegate.didRegister(deviceToken)
     }
   }
@@ -100,7 +119,7 @@
     withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void
   ) {
     var handled = false
-    for delegate in delegates {
+    for delegate in snapshotDelegates() {
       handled = delegate.willPresent(notification, completionHandler: completionHandler) || handled
     }
     if !handled {
@@ -113,18 +132,23 @@
     didReceive response: UNNotificationResponse,
     withCompletionHandler completionHandler: @escaping () -> Void
   ) {
+    let currentDelegates = stateLock.withLock {
+      // A delegate registering during delivery must see this response too.
+      pendingResponses.append(response)
+      return delegates
+    }
     var handled = false
-    for delegate in delegates {
+    for delegate in currentDelegates {
       handled = delegate.didReceive(response, completionHandler: completionHandler) || handled
     }
-    if !handled {
-      pendingResponses.append(response)
+    if handled {
+      removePendingResponses([response])
     }
     completionHandler()
   }
 
   public func userNotificationCenter(_ center: UNUserNotificationCenter, openSettingsFor notification: UNNotification?) {
-    for delegate in delegates {
+    for delegate in snapshotDelegates() {
       delegate.openSettings(notification)
     }
   }
@@ -132,7 +156,7 @@
   // MARK: - Called from NotificationsAppDelegateSubscriber
   public func didReceive(_ userInfo: [AnyHashable: Any], completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
     var handled = false
-    for delegate in delegates {
+    for delegate in snapshotDelegates() {
       handled = delegate.didReceive(userInfo, completionHandler: completionHandler) || handled
     }
     if !handled {