Iambia thwaitesii is a moth of the family Noctuidae first described by Frederic Moore in 1885.

The body is pale brown, but the head and thorax are marked with black.

Antemedial and postmedial double lines reduced to series of striae.

There is a broad sub-marginal waved black band form costa to vein 4.

The apical part of the submarginal band forming a prominent black patch.