Rubber seed oil is a high free fatty acid content, nonedible vegetable oil. The acid value of unrened rubber seed oil is about 34. Neither alkaline-catalyzed transesterication nor acid-catalysed esterication alone is suitable. A two-step esterication process, that is, acid esterication followed by alkaline transesterication was developed to convert the unrened rubber seed oil to its methyl esters and glycerol. The process parameters, such as quantity of catalyst and methanol used, reaction temperature, and reaction duration, are analysed. The properties of methyl esters of rubber seed oil are comparable to that of diesel. The performance and emission characteristics of biodiesel-diesel blends provide evidence that methyl esters of rubber seed oil are a suitable alternative fuel to diesel.