Diesel engines dominate the field of commercial transportation and agricultural machinery on account of its superior fuel efficiency. Cost and limited reserves of conventional fossil fuels have intensified the search for alternative fuels for use in internal combustion engines. A possible alternative engine fuel is vegetable oil because it is clean burning, renewable, non-toxic, biodegradable and environmentally friendly transportation fuel. It can be used in neat form without any modification of the engine. They can be produced from the plants grown in rural areas. Vegetable oils are produced from crops such as soybean, peanut, sunflower, cotton, jatropha, mahua, neem, coconut, linseed, mustard, karanja, rape and castor. However they cause serious problems such as carbon deposits buildup, poor durability, high density, high viscosity, lower calorific value, more molecular weight and poor combustion. These problems can be rectified by transesterification process. In this investigation the engine performance in a C.I engine using three vegetable oil esters like jatropha, mahua, and neem oils for various injection pressures and compared with diesel. The experimental work is carried out in a single-cylinder computerized diesel engine test rig, which develops 5.2 kW at 1500 rpm and loaded by eddy current dynamometer at various engine load conditions. From the experimental results, it is found that the performance of vegetable oil esters is similar to diesel. However, a slight increase is observed for specific fuel consumption. The harmful pollutants such as HC, CO, NOX and smoke are reduced in the vegetable oil esters compared to that of diesel fuel. From the investigation, it is also concluded that in terms of performance characteristics and emission levels, vegetable oil esters can be regarded as the best substitute for diesel fuel.