Alternate fuel research has been the topic of the highest priority in the context of depletion of fossil fuels at an alarming rate and increasing of pollution levels of the engines with conventional fuels. The high consumption of diesel fuel in not only in agriculture sector but also in transport sector compels for the substitution of diesel fuel with suitable, renewable energy resources. Alcohols and vegetable oils are the major alternate fuels for diesel fuel as they are renewable in nature. The disadvantages of alcohols (ethanol and methanol) with low cetane numbers and vegetable oils with low volatility and high viscosity call for the hot combustion chamber, provided by low heat rejection diesel engine. About 30% of the heat energy supplied to the engine is being rejected through the chamber walls to the coolant and hence all efforts of the researcher turned towards reducing the heat rejection to the coolant and keep the combustion chamber hot which is suitable for burning renewable fuels like alcohols and vegetable oils quite effectively. The recent biodiesel research in India receives its attention towards fish-oil based biodiesel. In the present work, biodiesel derived from the fishoil extracted from fish species was used as fuel in the diesel engine to investigate its performance. This project presents the results of an investigation carried out in studying the properties and behavior of methyl esters of fish oil and its blends with diesel fuel in a C I Engine. Engine tests have been carried out to determine the performance characteristics of the fish oil. The tests have been carried out in a 4-stroke, single cylinder, constant speed, direct injection diesel engine with different loads. The loads were varied from 0% to 90% of the maximum load in steps of 20%. The various blends of fish-oil biodiesel with diesel, B20, B40, B50, B60 were used in the experiments and the results show that brake specific fuel consumption and brake thermal efficiency were higher with B60fuel than that of diesel. The performance parameters like brake specific fuel consumption, brake thermal efficiency