Abstract Varying fuel injection strategies is one of the promising methods to reduce engine out emissions and improve its performance as injection characteristics have great influences on combustion process. Out of various injection strategies, injection rate shaping is potentially an effective technique to reduce emission from engines. Injection rate shaping helps in reducing NOx emissions and reduces combustion noise. This work investigates the effect of injection rate shaping on combustion and emission characteristics of a direct injection diesel engine fueled by biodiesel. The CFD simulations were performed using multi-dimensional KIVA-4 code coupled with CHEMKIN chemistry solver. A detailed chemical kinetics of methyl decanoate (MD) and methyl-9-decenoate (MD9D) with 112 species and 498 reactions were used as surrogate fuel for biodiesel. The injection rate shapes were varied in terms of boot length (long, medium and short boot length) and boot pressure (low, medium and high boot pressure) and it was found from the results that a trade-off between NOx and soot emissions were obtained for long boot length, and high boot pressure injection rate profiles.