The researchers have been forced to resort a new combustion concept like homogeneous charge compression ignition (HCCI) to meet future emission regulations and to minimize the burden of after treatment system. In this work, the fuel vaporizer which is maintained above the boiling point of biodiesel is used to prepare the external mixture for HCCI mode of operation. The prepared biodiesel vapor is mixed with intake air stream and the mixture is inducted into the engine cylinder. The experimental results obtained from HCCI mode of operation are compared with DI diesel and DI biodiesel mode of operation (DI @ 23⁰ before Top Dead Center (bTDC) and 200 bar nozzle opening pressure). From this investigation, it is found that the reduced ignition delay and the occurrence of combustion throughout the cylinder volume lead to lower NOx and PM emissions.