Phocaenopsis mantelli was named by Huxley (1859). Its type specimen is BMNH M11091, a limb element (right humerus), and it is a 3D body fossil. Its type locality is Awamoa Creek, which is in an Altonian coastal horizon in the Mount Harris Formation of New Zealand. It is the type species of Phocaenopsis.

It was considered a nomen dubium by Fordyce and de Muizon (2001).