In order to improve an oil separator unit, in particular an oil separator unit provided for vehicle drives, comprising an oil separator housing with a drainage system and a check valve unit which is formed from a valve seat and a valve element which comprises a valve member of an umbrella-like design and consisting of an elastomer, in such a manner that it can be produced as inexpensively as possible, on the one hand, and, on the other hand, the wear on the valve element is, however, considerably reduced or occurs to as low a degree as possible, it is suggested that the valve member of the valve element be held on an insert part and that the insert part be insertable, for its part, into an insert part receptacle in a valve housing.