Today, the required energy of thermal desalination is widely supplied by power generation cycles as dual-purpose plants. One of the most considerable issues in combining gas turbine cycle (GT) with thermal desalination is how the operating parameters of GT affect technical and economic aspects of power and water production. Therefore, some researchers have studied dual-purpose plants from the thermodynamic point of view without economic or thermoeconomic considerations. According to the lack of studies in this area, in this paper, a dual-purpose plant is modeled which consisted of a GT with and without an air preheater (APH), heat recovery steam generator (HRSG) and multi-effect evaporation thermal vapor compression desalination (METVC). The system is supposed to supply 40 MW of power and 14,000 m(3)/day of fresh water for an industrial plant near the seashore in the south of Iran. After the simulation stage, a thermoeconomic analysis is performed and, then, a heuristic optimization algorithm, namely, multi-objective genetic algorithm (MOGA) is applied in order to achieve the optimal design. Eventually, it could be concluded that, by applying the optimization approach and using APH, the total cost of products decreases by 19% while the exergy efficiency of the combined cycle increases by 19%. (C) 2011 Elsevier B.V. All rights reserved.