The optimization problem of a combined heat pump cycle made of two endoreversible Carnot heat pump cycles in series without intermediate reservoirs is investigated using finite-time thermodynamics. The fundamental relation between heating quantity and coefficient of performance (COP) of the combined cycle is derived. Relations are also derived between the SRHP (specific rate of heat pumping), the average rate of heat pumping per unit of total heat-transfer surface area and the COP for reciprocating and stable flow models of combined cycles. The results obtained from this paper may be extended to an endoreversible, combined heat pump cycle formed by more than two endoreversible Carnot heat pump cycles.