diff --git a/booru_viewer/gui/app.py b/booru_viewer/gui/app.py
index 8928cce..2f9f497 100644
--- a/booru_viewer/gui/app.py
+++ b/booru_viewer/gui/app.py
@@ -1433,15 +1433,21 @@ class BooruApp(QMainWindow):
                 cp = str(cached_path_for(post.file_url))
                 if cp == self._preview._current_path:
                     self._preview.clear()
+                    if self._fullscreen_window and self._fullscreen_window.isVisible():
+                        self._fullscreen_window._viewer.clear()
+                        self._fullscreen_window._video.stop()
             self._status.showMessage(f"Blacklisted: {tag}")
             self._do_search()
         elif action == bl_post_action:
             self._db.add_blacklisted_post(post.file_url)
-            # Clear preview if this is the previewed post
+            # Clear preview/slideshow if this is the previewed post
             from ..core.cache import cached_path_for
             cp = str(cached_path_for(post.file_url))
             if cp == self._preview._current_path:
                 self._preview.clear()
+                if self._fullscreen_window and self._fullscreen_window.isVisible():
+                    self._fullscreen_window._viewer.clear()
+                    self._fullscreen_window._video.stop()
             self._status.showMessage(f"Post #{post.id} blacklisted")
             self._do_search()