This study presents the production of coconut oil biodiesel (COB) by using the trans-esterification process. The combustion efficiency and exhaust gas emission of an agricultural diesel engine using COB compared with diesel fuel were investigated. The 4-stroke cycle, single-cylinder diesel engine with naturally aspirated air and fuel injection degree 24 bTDC has been tested at a compression ratio of 17. The engine test was evaluated under the speed at 1,500 rpm with various load tests at 3, 6, 9 and 12 kg. The %yield of COB from the production process is found to be 90.52%. The fatty acid content is 75.85% in COB using Gas Chromatography. COB consists of specific gravity, viscosity, cetane index, and heat value of the fuel were measured according to ASTM standards. A cetane index of COB provides a lower value than that of diesel fuel. It leads to the engine using COB obtaining higher specific fuel consumption value than diesel fuel by 19.67%. However, it is noticed that COB provides outstanding physical properties in lower viscosity than diesel fuel with its containing 47.52% Lauric acid fatty acids, Myristic acid 18.37%, and Palmitic acid 9.24%. COB components with a carbon chain shorter than other fuels result in the lowest fuel calorific value. The combustion engine performance using COB shows a shorter ignition time delay than that using diesel fuel. The COB properties have a direct influence on the reduction of emissions and smoke from the agricultural diesel engine compared with diesel fuel used.