Diaphorodoris mitsuii is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusc in the family Calycidorididae.

It is reported from South Korea, Japan and Hong Kong.

[3] Specimens from Australia, Indonesia and the Red Sea are likely to be distinct, unnamed, species of Diaphorodoris.

Branchial plumes 6, small, simply pinnate, completely retractile within a cavity with smooth margin.

Foot produced behind in a fairly long tail, the anterior end abruptly rounded and simply labiate.