diff --git a/components/subresource_filter/android/java/src/org/chromium/components/subresource_filter/AdsBlockedDialog.java b/components/subresource_filter/android/java/src/org/chromium/components/subresource_filter/AdsBlockedDialog.java
--- a/components/subresource_filter/android/java/src/org/chromium/components/subresource_filter/AdsBlockedDialog.java
+++ b/components/subresource_filter/android/java/src/org/chromium/components/subresource_filter/AdsBlockedDialog.java
@@ -135,6 +135,12 @@ public class AdsBlockedDialog implements ModalDialogProperties.Controller {

     @CalledByNative
     void dismiss() {
+        // The native AdsBlockedDialog is being destroyed. Proactively cancel any
+        // pending show task and clear the native pointer here, because
+        // ModalDialogManager.dismissDialog() will early-return without invoking
+        // onDismiss() if the dialog has not yet been shown or queued.
+        mDialogHandler.removeCallbacksAndMessages(null);
+        mNativeDialog = 0;
         mModalDialogManager.dismissDialog(mDialogModel, DialogDismissalCause.DISMISSED_BY_NATIVE);
     }

@@ -153,7 +159,7 @@ public class AdsBlockedDialog implements ModalDialogProperties.Controller {
     // ModalDialogProperties.Controller implementation.
     @Override
     public void onClick(PropertyModel model, @ButtonType int buttonType) {
-        assert mNativeDialog != 0;
+        if (mNativeDialog == 0) return;
         if (buttonType == ButtonType.POSITIVE) {
             AdsBlockedDialogJni.get().onAllowAdsClicked(mNativeDialog);
         }
@@ -167,6 +173,7 @@ public class AdsBlockedDialog implements ModalDialogProperties.Controller {
     @Override
     public void onDismiss(PropertyModel model, @DialogDismissalCause int dismissalCause) {
         mDialogHandler.removeCallbacksAndMessages(null);
+        if (mNativeDialog == 0) return;
         AdsBlockedDialogJni.get().onDismissed(mNativeDialog);
         mNativeDialog = 0;
     }