diff --git a/Lib/test/test_io/test_fileio.py b/Lib/test/test_io/test_fileio.py
index 21a160904a7f1e..14db757964cf3d 100644
--- a/Lib/test/test_io/test_fileio.py
+++ b/Lib/test/test_io/test_fileio.py
@@ -62,6 +62,10 @@ def testSeekTell(self):
         self.f.seek(-5, 2)
         self.assertEqual(self.f.tell(), 15)
 
+    def testSeekableAfterFailedSeek(self) -> None:
+        self.assertRaises(OSError, self.f.seek, -1)
+        self.assertTrue(self.f.seekable())
+
     def testAttributes(self):
         # verify expected attributes exist
         f = self.f
diff --git a/Misc/NEWS.d/next/Library/2026-10-18-17-26-00.gh-issue-159677.fIoSk1.rst b/Misc/NEWS.d/next/Library/2026-10-18-17-26-00.gh-issue-159677.fIoSk1.rst
new file mode 100644
index 00000000000000..93feb6c41c545a
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-10-18-17-26-00.gh-issue-159677.fIoSk1.rst
@@ -0,0 +1,2 @@
+Fix :class:`io.FileIO` ``seekable`` being cached as false because of an invalid
+argument to :meth:`!io.FileIO.seek`
diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c
index e5cd7aca5de2f1..974369f107e927 100644
--- a/Modules/_io/fileio.c
+++ b/Modules/_io/fileio.c
@@ -1013,7 +1013,7 @@ portable_lseek(fileio *self, PyObject *posobj, int whence, bool suppress_pipe_er
     _Py_END_SUPPRESS_IPH
     Py_END_ALLOW_THREADS
 
-    if (self->seekable < 0) {
+    if (self->seekable < 0 && (res >= 0 || errno == ESPIPE || posobj == NULL)) {
         self->seekable = (res >= 0);
     }