diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 043a4ab5a52a6f..a738e25684c481 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -1785,7 +1785,7 @@ def getmember(self, name):
            than once in the archive, its last occurrence is assumed to be the
            most up-to-date version.
         """
-        tarinfo = self._getmember(name)
+        tarinfo = self._getmember(name.rstrip('/'))
         if tarinfo is None:
             raise KeyError("filename %r not found" % name)
         return tarinfo
diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py
index 06fb97212d8567..a4b63ff82b3ae3 100644
--- a/Lib/test/test_tarfile.py
+++ b/Lib/test/test_tarfile.py
@@ -219,6 +219,25 @@ def test_fileobj_symlink2(self):
     def test_issue14160(self):
         self._test_fileobj_link("symtype2", "ustar/regtype")
 
+    def test_add_dir_getmember(self):
+        # bpo-21987
+        self.add_dir_and_getmember('bar')
+        self.add_dir_and_getmember('a'*101)
+
+    def add_dir_and_getmember(self, name):
+        with support.temp_cwd():
+            with tarfile.open(tmpname, 'w') as tar:
+                try:
+                    os.mkdir(name)
+                    tar.add(name)
+                finally:
+                    os.rmdir(name)
+            with tarfile.open(tmpname) as tar:
+                self.assertEqual(
+                    tar.getmember(name),
+                    tar.getmember(name + '/')
+                )
+
 class GzipUstarReadTest(GzipTest, UstarReadTest):
     pass
 
diff --git a/Misc/NEWS.d/next/Library/2021-12-28-11-55-10.bpo-21987.avBK-p.rst b/Misc/NEWS.d/next/Library/2021-12-28-11-55-10.bpo-21987.avBK-p.rst
new file mode 100644
index 00000000000000..305dd16d53b495
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-12-28-11-55-10.bpo-21987.avBK-p.rst
@@ -0,0 +1,2 @@
+Fix an issue with :meth:`tarfile.TarFile.getmember` getting a directory name
+with a trailing slash.