The present study examined the performance and emission characteristics of a single-cylinder, four-stroke, water-cooled, diesel engine with a power output of 3.7 kW and a constant speed of 1500 rpm. The engine was fueled with palm oil biodiesel (POBD) and blended palm oil biodiesel (BPOBD) in both mono and dual fuel modes, with and without biogas. The results were then compared to diesel fuel. The study found that as the mass flow rate of biogas increased, the energy proportion of BPOBD decreased due to the low calorific value of biogas. However, at high braking power, the BSFC of POBD/BD100 was lower than that of diesel in mono fuel mode. Furthermore, as the supply of biogas to the engine increased, the BSFC of all mixed fuels decreased. Additionally, increasing the percentage of biodiesel in the monofuel blend led to a continual decrease in CO emissions. Similarly, increasing the amount of biodiesel in the monofuel blend resulted in a continual decrease in HC emissions. However, in comparison to providing biogas in dual fuel mode, the use of mixed biodiesel in monofuel mode emitted greater amounts of CO2.