Kyphosus cornelii is similar to the silver drummer but it has a slender body shape when compared to other drummer species. The rear edge of the pectoral fins is an orange-yellow colour. The upper and lower margins of the caudal fin have a pale margin with a dusky submarginal bar. The main difference from the silver drummer is the more distinctly forked tail and the palecaudal fin margin and the suborbital dark moustache. It attains a maximum total length of.
Kyphosus cornelii is found on coral and rock reefs at depths of in inshore waters. It feeds largely on seaweed, especially red algae. They are territorial and defend a patch of seaweed, gardening the patch to keep the seaweed short so that they can see other Western buffalo bream. The fish will steal food from other patches of other fish, especially if the seaweed grows too tall. It can occur in mixed schools with silver drummers.