Animal fat, raw, and used vegetable oils have been explored to make bio-diesel (mono alkyl esters of long chain fatty acid) in order to substitute the dwindling supplier of conventional petro-diesel fuels. In the present investigation custard apple (Annoma Squamosha), seed oil (non-edible) was Transesterified with methanol in the presence of sodium hydroxide as catalyst. The transesterification reaction was carried out at 650C for an hour, keeping the molar ratio of methanol to oil at 6:1 and sodium hydroxide concentration of 0.5 wt % of the oil. The yield of fatty acid methyl esters produced under operating conditions was 86.4 wt%. The methyl ester produced by this reaction was analyzed to ascertain suitability as bio diesel fuels.