Fossil fuel is one of the sources leading to the increasing greenhouse gas that causes global warming. It is also seen that the volume of oil discovered worldwide every five years is decreasing. Finding ways to replace petrol-diesel with biodiesel for use in internal combustion engines to reduce CO2 and overcome the diminishing supply of crude oil has attracted many researchers. Viet Nam is a country known as one of the world's largest producers of catfish. We mix biodiesel produced from Vietnamese pangasius fish fat with petrol-diesel at four blend ratios of 0%, 20%, 40%, and 60% to produce samples labeled, B0, B20, B40, and B60, respectively. These biodiesel blends were then used to operate a petrol-diesel engine for experimental investigation. The results show that the torque and power would decrease as the biofuel ratio increased. However, the rate of decrease of these parameters did not exceed 16%, even when the ratio of biofuel in the biodiesel was up to 60%. The average power reduction of biodiesel blends was only about 8.70%. In terms of exhaust emissions, there was a significant reduction of CO, NOx, HC, CO2, and smoke opacity when biodiesel was used. The CO, CO2, and smoke opacity reduction was about 64.3%,15.1%, and 23.2% for the B60 fuel. In addition, the results also indicate that it is entirely possible to use biofuel produced from pangasius fish fat for internal combustion engines without changing the engine structure.