Renewable energy sources (RES) can be a significant source of profit. However, different RES projects can bring various benefits to their investors, raising the question—Which RES project to select? The objective of this study is to provide answers to two questions: (1) Which factors/criteria should be used in the RES project selection procedure; (2) Which RES project should the investor select out of a group of prospective projects? The study was conducted in a company operating in the energy sector in Serbia. In order to find answers to the above-mentioned questions, the study employed a hybrid methodology integrating the SWOT (Strengths, Weaknesses, Opportunities, Threats) analysis and the Analytical Hierarchy Process (AHP). First, the Company's management defined the goal and project alternatives. The goal was to select an optimal RES project suitable for the specific circumstances in the Serbian energy sector, and also for the Company's potentials. The alternatives included: a hydro energy project, a solar energy project, a wind energy project (WEP), and a biomass energy project. Then, the decision-making group was formed, consisting of four company's experts (hereinafter collectively referred to as “the decision-makers”), of different professional backgrounds and affiliations. Second, the decision-makers employed SWOT analysis on the RES projects in Serbia to obtain the decision-making criteria. The decision-making procedure has to be based on 20 SWOT factors. However, each criterion is not of equal importance for investors. This shortcoming has been overcome by introducing AHP. Pairwise comparison was performed using the Expert Choice 2000 software. According to the results, the top-ranking project is the WEP.