In search of solution to the harmful ecological problems due to toxicity and non-biodegradability posed by conventional transformer insulation oil (mineral oil), the production of transformer oil from castor seed oil (vegetable oil) was carried out. The oil was extracted using N-hexane and was refined. The transformer oil was produced by trans-esterification and was characterized using American Society for Testing Material (ASTM) standard test. The solvent employed gave good yield of oil from the seeds. The results of characterization show that the density 0.987 (g ml–1), viscosity7.01 (cst), Flash Point 253oC and dielectric strength of 23(KV) values, of Castor seed oil as transformer oil produced under optimized conditions meet the ASTM standard and was within the acceptable limits as transformer oil. These showed that castor seed oil is a potential feed stock for production transformer oil.