In the present study, the operating temperatures of the mechanical heat pump in waste heat recovery were investigated to elucidate the effect of control parameters such as compressor speed, wastewater temperature and mass flow rate. The experimental trials were performed using the Taguchi L27 full factorial orthogonal array, and the results were optimized for compressor suction gas temperature, compressor discharge gas temperature, temperature difference of water entering and leaving the evaporator, temperature difference of water entering and leaving the condenser, evaporation temperature, and condensation temperature. Analysis of variance was conducted to determine the effect of the control factors on the operating temperatures of mechanical heat pump. The analysis results show that the wastewater temperature was the most significant factor on compressor suction gas temperature and discharge gas temperature. The compressor speed has shown a meaningful effect on the temperature difference of water entering and leaving from condenser. The nominal levels of control factors and the optimal temperatures were specified for the studied experimental parameters. Prediction models were developed for the operating temperatures through the Taguchi method and the operating temperatures were predicted with a mean squared error less than 12%.