In this paper, a humidification-dehumidification desalination HDH cycle with direct contact dehumidifier is coupled with a heat pump. The heat pump is introduced in order to simultaneously supply the cooling and heating loads of the HDH cycle. Next, by implementing a mathematical model, the performance of the system is investigated under different working conditions. To incorporate the humidifier and dehumidifier effectiveness into the theoretical modeling, the e-NTU correlation of the heat and mass transfer device is utilized. Performance parameters such as specific electrical energy consumption (SEEC), recovery ratio (RR) and coefficient of performance (COP) are employed for evaluating the system performance. The fully coupled condition of the HDH system with no extra cooling or heating scenarios is investigated. It is shown that a given saline water and freshwater temperatures, a fully coupled HDH system with the heat pump without adding the extra cooler can be achieved by alternating mass flow rate ratio of either seawater to freshwater or seawater to dry air.