This paper presents thermodynamic and thermoeconomic analyses as well as optimization of a re-compression supercritical CO₂ cycle. A gas turbine cycle is adapted as a model to an existing plant in order to generate additional power in Gaziantep Municipal Solid Waste Power Plant. The total capital cost rate and the total cost rate of the GT cycle are found to be 20.47 $/h and 77.14 $/h, respectively utilizing a well-known method, SPECO. The net power output, the energy efficiency, the exergy efficiency, the total cost rate and the total capital cost rate of the GT cycle are optimized by +1.73 %, +3.21 %, +2.45 %, -1.11 % and -1.64 %, respectively by using the non-dominated sorting genetic algorithm method (NSGA-II) in MATLAB environment. This paper provides an originality such that the optimization as well as thermodynamic and thermoeconomic analyses is performed simultaneously for an existing MSW power plant, which can be stressed that there are scarce amounts of studies related on this field. Moreover, as another novelty, it can be emphasized that net power output of such like plants which have similar capacity can be improved with almost +20 % by using the developed model and NSGA-II optimization method.