In this work, microalgae–microbial fuel cell (MMFC) was used as an alternative method to treat cafeteria waste in Indonesia to produce electricity and microalgal biomass simultaneously. The organic contents from cafeteria waste were used as substrates by Saccharomyces cerevisiae. Spirulina platensis acted as an oxygen producer for oxygen reduction reaction on the cathode side. A salt bridge was used as a separator and ion exchanger. Yeast (Saccharomyces cerevisiae) was used as an anode biocatalyst because of its availability, resistance to extreme weather, and ease of culture and incubation. A voltage of 0.17 V and current density of 400 mA m⁻² were obtained using the MMFC system. Meanwhile, the power density and maximum power density (MPD) reached 73 and 98 mW m⁻², respectively. The MMFC systems can easily reduce the chemical oxygen demand to 60% and the total dissolved solid to 82.83%. Meanwhile, the microalgae growing on the cathode side reached 0.74 g L⁻¹ by utilizing CO₂ from the anode side. The MPD of the MMFC system was 2.38 folds higher than that of the MFC system (without microalgae) and 1.58 times higher than that of the MMFC system that used a commercial membrane. These advantages make the MMFC system for cafeteria waste highly suitable for use in countries with large populations or developing countries.