This study presents effect of injection timing on performance, combustion and emission characteristics of mahua biodiesel (Madhuca indica) and its blends with pure diesel on a 4 stroke tangentially vertical single cylinder (TV 1) direct injection diesel engine. At injection timing of 22° bTDC, blend B25 (25% mahua biodiesel and 75% pure diesel, by vol) gave optimum performance, which is very close to pure diesel. Thus B25 fuel can be effectively used in a diesel engine as an alternative fuel without any modification in the engine. Diesel (25%) thus saved will greatly help the interests of railways in meeting the demand for fuel, as diesel trains are operated at maximum load condition.