This paper reports the investigation of jatropha curcas seeds oil as an alternative option to replace mineral oil in power transformers. This product has several advantages that recommend both its production and usage over that of other vegetable oils as crude palm oil and rape-seeds oil because it may be grown on marginal or degraded soils thus avoiding the need to utilize those more fertile soils currently being used by smallholders to grow their staple crops; and it will readily grow in areas where annual rainfall levels are significantly lower than those required by other species such as oil palm, rape-seeds oil, sunflower oil, soybeans oil, corn oil and others. For instance, these plants can be grown on all soil types in Indonesia, even on barren soil. The barren soil types can be found in many parts of eastern Indonesia that remain untapped because of the difficulty planted with other crops. Moreover, jatropha curcas oil is non-food crops. Jatropha curcas oil is processed by alkali base catalyzed esterification process using potassium hydroxide (KOH) to produce jatropha curcas methyl ester oil (JMEO) that is a product the viscosity and acidity are acceptable for high voltage equipment especially in power transformer. The physicochemical (water content, viscosity, acidity...) and electrical (dielectric strength) properties of JMEO were measured. For comparison, we also measured breakdown voltage of mineral oil (MO) in the same experimental conditions. The obtained results show that the average AC breakdown voltages of JMEO and MO are too close.