Life Cycle Assessments (LCAs) of thermoelectric plants frequently focus on impacts related to fuel and water consumption. The purpose of this research was to determine the environmental impact of the chemicals used for water conditioning in a Combined-Cycle Gas Turbine (CCGT) plant in Mexico. An LCA of the electricity generation process was carried out using the SimaPro software with the ReCiPe method, which includes 18 midpoint environmental impact categories. The process was broken down into stages, which were analyzed separately. To complete the study, an analysis of the fuel cycle and the materials used for maintenance works were included. Results showed that the most affected impact categories were water depletion (9.77 × 10−1 m3/MWh), due mainly to the high volume of water consumption in the cooling systems and the reverse osmosis process; freshwater, marine, and terrestrial ecotoxicity (1.59 × 10−2 kg 1,4 -DB eq/MWh), and human toxicity (1.1 × 10−1 kg 1,4-DB eq/MWh)—due to the production and consumption of the chemicals used. One such chemical is hydrazine, which is a highly toxic compound to humans and other living organisms. It is worth mentioning that traces of some chemicals in wastewater discharges could be considered as emerging pollutants because of their potential health hazards, which have not been reported yet.