diff --git a/telethon/_misc/html.py b/telethon/_misc/html.py
index c17f6f7c..cdf4ced4 100644
--- a/telethon/_misc/html.py
+++ b/telethon/_misc/html.py
@@ -47,6 +47,8 @@ class HTMLToTelegramParser(HTMLParser):
             EntityType = _tl.MessageEntityUnderline
         elif tag == 'del' or tag == 's':
             EntityType = _tl.MessageEntityStrike
+        elif tag == 'tg-spoiler':
+            EntityType = _tl.MessageEntitySpoiler
         elif tag == 'blockquote':
             EntityType = _tl.MessageEntityBlockquote
         elif tag == 'code':
diff --git a/telethon/_misc/markdown.py b/telethon/_misc/markdown.py
index 8dc82701..3b62c995 100644
--- a/telethon/_misc/markdown.py
+++ b/telethon/_misc/markdown.py
@@ -19,6 +19,7 @@ DELIMITERS = {
     _tl.MessageEntityCode: ('`', '`'),
     _tl.MessageEntityItalic: ('_', '_'),
     _tl.MessageEntityStrike: ('~~', '~~'),
+    _tl.MessageEntitySpoiler: ('||', '||'),
     _tl.MessageEntityUnderline: ('# ', ''),
 }