In the current study, combustion characteristics were evaluated using mahua biodiesel blends at different compression ratios on a direct injection CI engine. Non edible mahua oil was transesterified into biodiesel by two stage technique. Combustion parameters were evaluated for B5, B10 and B20 blends of mahua biodiesel with diesel and they were compared with straight diesel at compression ratios of 16, 17 and 18.Compression ratio was varied without altering the combustion chamber geometry and the static spill timing was set to 23° bTDC. Parameters like In cylinder pressure, heat release rate, rate of pressure rise and cumulative heat release were evaluated in this study at 100% engine loading conditions. Higher peak cylinder pressure and heat release was observed at higher compression ratios. The ignition delay of the blends were slightly higher compared to diesel at all CR tested. Peak cylinder pressure of the blends was slightly higher at CR 18. The ignition delay was also observed to be lower at higher compression ratio. The peak pressure was observed closer to TDC at higher compression ratios for all fuels tested.