Coconut oil is an alternative raw material of biodiesel production, due to the plentiful availability of coconuts especially in Indonesia. To utilize the availability of coconut, biodiesel will be made from coconut oil. Vegetable oil has a viscosity that is 20 times higher than the fossil diesel fuel which affects the fuel atomization in the diesel engine burning room, therefore it needs to be reacted and converted to methyl ester (biodiesel) with methanol and catalyst (KOH) through a transesterification process using a heater. In this research, the first step in a biodiesel production is started from coconut oil VCO with 1200 ml volume which was processed in transesterification using methanol 15% from volume of oil and the catalyst used is Potassium Hydroxide (KOH) with a ratio of 1% of the oil volume. The process of mixing coconut oil with a mixture of methanol and KOH catalysts uses four reaction time variation levels (30 minutes, 60 minutes, 90 minutes, 120 minutes) and two temperature variations (55° C and 65° C). The results of this study showed that the character of biodiesel is influenced by temperature and reaction time. The optimum treatment combination in process transesterification is temperature at 65ºC and 120 minutes, therefore, it can be concluded that the higher variation of time and temperature the more biodiesel obtained, along with the higher decrease of transesterification reaction variation, density value, and viscosity.