diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index 5f128320d25..42f48e1d630 100755
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -1404,6 +1404,9 @@ class _PlainTextDoc(TextDoc):
 def pager(text):
     """The first time this is called, determine what kind of pager to use."""
     global pager
+    # Escape non-encodable characters to avoid encoding errors later
+    encoding = sys.getfilesystemencoding()
+    text = text.encode(encoding, 'backslashreplace').decode(encoding)
     pager = getpager()
     pager(text)
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 7366cd84531..57460745636 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -84,6 +84,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #21398: Fix an unicode error in the pydoc pager when the documentation
+  contains characters not encodable to the stdout encoding.
+
 - Issue #16531: ipaddress.IPv4Network and ipaddress.IPv6Network now accept
   an (address, netmask) tuple argument, so as to easily construct network
   objects from existing addresses.