diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 068aa13ed70356..1fd77786176645 100644
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -1616,14 +1616,19 @@ def _apply_pax_info(self, pax_headers, encoding, errors):
         """Replace fields with supplemental information from a previous
            pax extended or global header.
         """
+        real_size_updated = False
         for keyword, value in pax_headers.items():
             if keyword == "GNU.sparse.name":
                 setattr(self, "path", value)
             elif keyword == "GNU.sparse.size":
                 setattr(self, "size", int(value))
+                real_size_updated = True
             elif keyword == "GNU.sparse.realsize":
                 setattr(self, "size", int(value))
+                real_size_updated = True
             elif keyword in PAX_FIELDS:
+                if keyword == "size" and real_size_updated:
+                    continue
                 if keyword in PAX_NUMBER_FIELDS:
                     try:
                         value = PAX_NUMBER_FIELDS[keyword](value)
diff --git a/Misc/NEWS.d/next/Library/2025-07-13-12-37-49.gh-issue-136601.ZBiMIN.rst b/Misc/NEWS.d/next/Library/2025-07-13-12-37-49.gh-issue-136601.ZBiMIN.rst
new file mode 100644
index 00000000000000..23080e4c70053f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-07-13-12-37-49.gh-issue-136601.ZBiMIN.rst
@@ -0,0 +1 @@
+Always set ``TarInfo.size`` to the real file size for sparse files.