Direct contact membrane distillation (DCMD) powered by solar energy is an attractive solution to mitigate freshwater supply problems. This paper presents an investigation on performance and cost of a 111 MWe solar power tower (SPT) plant integrated with DCMD system. The SPT plant comprised of an evaporative cooling with seawater as cooling agent in the condenser. Additionally, warm seawater leaving the condenser was introduced into DCMD system as feed water. For SPT plant, simulations revealed that an increment in incident solar power enhanced the electricity production and consequently the cooling water requirements. Annual gross electric output and cooling water requirements were estimated to be 493.8 GWh and 1,422,364 m(3), respectively. Whereas the energy cost was estimated to be 13.03 cents per kWh. Furthermore, a mathematical model was developed and solved for evaluating the DCMD system. The model was validated by means of the experimental data. In DCMD system, permeate flux and evaporation efficiency increased when feed water temperature was increased. However, specific thermal energy consumption decreased with an increase in feed water temperature. The average freshwater production by the proposed system was estimated up to 40,759 L/day with a cost of $0.392/m(3).