The effect of compression ratio on combustion, performance, and emission characteristics of a direct injection single cylinder four stroke variable compression ratio multi fuel engine when fueled with corn oil methyl ester (COME) and palm oil methyl ester (POME) is investigated and compared with petroleum based diesel fuel (PBDF). The suitability of COME and POME as biofuels has been studied in this research. Biodiesels produced from corn oil and palm oil by transesterification process has been used in this study. Experiments were conducted at constant speed of 1500 rpm, full load, and at compression ratio of 17:1, 18:1, and 19:1. The effect of compression ratio on heat release rate, specific fuel consumption, and exhaust gas emissions has been investigated and presented. The fuels which gave best performance when used in engine have been identified by optimum compression ratio. The results indicate that shorter ignition delay, maximum rate of combustion pressure, and lower heat release rate at higher compression ratio were observed for POME when compared to PBDF. The brake thermal efficiency of POME was found to be maximum than PBDF at full load for all compression ratio. Exhaust gas temperature is low for biodiesels when compared to PBDF from compression ratio 17:1 to 19:1. The emission of CO, CO₂, and HC dropped with compression ratio 17:1 and it slightly increased when compression ratio is increased. The engine performance was found to be optimum when using POME as fuel, at compression ratio 19:1 during full load condition.