Ethmia millerorum is a moth in the Depressariidae family. It is found in Costa Rica, where it has been recorded from 1,150 to 1,300 meters in the Cordillera Volcánica de Guanacaste. The habitat consists of rain forests. The length of the forewings is 10.9–11.9 mm. The ground color of the forewings is white with a large quadrate dorsal purplish coppery blotch at the posterior half from near the base to the tornus. The costal area has four blackish spots at the base and there is one distinct spot at the dorsum. The hindwing ground colour is whitish, but darker towards the margin.