The world today is facing the effect of the dependence on fossil fuels. Also, the rate of consumption of Fossil derived fuels is alarming. The use of non-conventional energy sources is to be increased so as to tackle the global climatic changes, environmental pollution and also to lower down the rate of depletion of fossil fuels. The urgent need to replace the petroleum products having harmful emissions has leaded us to the Biodiesel. Biodiesel is a well-known alternative for diesel with an advantage over the later because of its biodegradable, less toxic nature, superior lubricity, better emission characteristics and in a way environment friendly. The present study focuses on the comparative study and analysis of performance and emission characteristics of a light duty diesel engine on blends of Fish oil Biodiesel in Diesel and Calophyllum Inophyllum Oil Biodiesel in Diesel. The blends taken for the study are 5% (V/V), 10% (V/V), 15% (V/V) of fish oil methyl ester in diesel as FOMED05, FOMED10, FOMED15 and 5% (v/v), 10% (v/v), 15% (v/v) of calophyllum inophyllum oil methyl ester in diesel as COMED05, COMED10, COMED15 respectively. The comprehensive assessment was done to investigate the effects of blends on brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), Exhaust gas temperature, Unburned Hydrocarbon emission (UHC), Carbon monoxide Emission (CO), Oxides of nitrogen emission (NOx) and Smoke opacity.