Hydropower has historically been the predominant source in the Brazilian electrical system. The mitigation of the inherent uncertainties of this source has been partially addressed through the operation of thermal power plants. Currently, wind and solar photovoltaic plants have dominated expansions in the generation capacity due to concerns about climate change, government policies, and reduced investment costs. Natural gas-fired thermal power plants, being more flexible and less polluting, will continue to play a crucial role in mitigating the uncertainties associated with renewable sources. Thermal power plants projects require significant investments and therefore making a thorough financial feasibility analysis is essential to ensure the success and financial return of power generation companies. This study proposes to analyze the financial feasibility, through the Free Cash Flow method, of the natural gas-fired thermal power plant project, Porto de Sergipe I. The results of the study presented a positive financial return, but sensitivity studies indicate risks related to variations in the Weighted Average Cost of Capital (WACC) and the investment payback period.