Pempherus poeyi has a moderately deep, highly compressed body with a straight dorsal profile.

They vary in colour from light yellowish brown, slightly duskier dorsally, to blackish on entire upper flanks and tail.

Pempheris poeyi is nocturnal and spends the day in schools in caves, under ledges, or among dense branching coral.

[1] This species is found at depths between 2 and 20 metres (6.6 and 65.6 ft)It comes out of its sheltering places at night to feed on zooplankton in the water column.

[2] Pempheris poeyi was described by Tarleton Hoffman Bean in 1885,[4] he found the type among specimens collected by Felipe Poey in Cuba and deposited in the United States National Museum.