Used-cooking oil is a waste product after using cooking oil 3-4 times. The disposal of used cooking oil directly into waterways causes environmental pollution. Bacillus cereus and Pseudomonas aeruginosa are well known to be effective in degrading used-cooking oil. Biodegradation of used-cooking oil is needed to reduce the pollution created by the current disposal of oil. This study aimed to determine the capability of single and mixed cultures of B. cereus InaCC B284 and P. aeruginosa InaCC B290 to degrade used cooking oil. The biodegradation process was carried out using Bushnell Haas Broth (BHB) containing 25% (v/v) used cooking oil for 23 days at room temperature (27-30°C). Optical density (OD), pH, dissolved oxygen (DO), and fatty acid content were measured throughout the biodegradation process. Different bacterial treatments resulted in significant increases to the OD (p < 0.05) and significant decreases to the pH (p < 0.05) during biodegradation. Qualitative and quantitative fatty acid analysis performed by gas chromatography revealed that a single culture of B. cereus InaCC B284 was capable of degrading seven types of fatty acids, a single culture of P. aeruginosa InaCC B290 was capable of degrading four types of fatty acids, and mixed cultures were capable of degrading 11 types of fatty acids.