Polygrammodes nonagrialis is a moth in the Crambidae family. It is found in Peru. The wingspan is about 40 mm. Adults are pale ochreous grey-brown, the forewings with a fuscous discoidal lunule. There are traces of a curved postmedial seriesof fuscous points in the interspaces and of fuscous subterminal streaks towards the apex. The hindwings are whitish, tinged with brownish towards the termen.