The growing demand of diesel power generators in Iran has led to air pollution. Hence, it is necessary to ascertain the level of performance and emissions of the diesel power generators fueled with biofuels. For the first time, in this study, the effect of biodiesel from waste cooking oil and diesel fuel blends (B0, B20, B50, B80 and B100) on the performance (brake power, brake torque, BSFC, brake thermal efficiency and exhaust gas temperature) and emission characteristics (CO and NOx) of a diesel power generator model CAT3412 was investigated. The experiments were conducted at rated engine speed 1530 rpm and various engine loads (25%, 50%, 75% and 100%). The results of the study showed an increase in brake power, brake torque, BTE and NOx emission and a reduction trend in BSFC and CO emission at higher engine loads for all the biodiesel-diesel blends. In addition, the research results indicated that B20 and B50 fuel blends in terms of performance emission characteristics could be recognized as the potential candidates to be certificated for usage in the diesel power generator.