The effect of microwave enhanced plasma (MW Plasma) on diesel spray combustion was investigated inside a constant volume high pressure chamber. A microwave-enhanced plasma system, in which plasma discharge generated by a spark plug was amplified using microwave pulses, was used to introduce plasma. Initially, the plasma was introduced to the diesel spray before the occurrence of auto-ignition, to understand the effect of additional oxidizer entertainment on ignition delay of diesel spay. High speed imaging of natural luminosity indicated an earlier appearance of flame in the with-plasma cases compared to the respective without-plasma conventional operation. These results corresponds well to the behavior of the heat-release rates, suggesting a reduction-effect by MW plasma on the ignition delay of diesel combustion. Later, the plasma was introduced downstream the flame lift-off and in the soot cloud to estimate the soot reduction effect by plasma. Planar laser induced incandescence diagnostics were performed with laser sheet formed from 532 nm YAG laser, to estimate LII signal intensity. A semi-quantitative comparison was made between without-plasma conventional operation and with-plasma operation with different levels of input energy of MW plasma. Results indicated that plasma can effectively reduce the soot; with increase in the MW energy the soot reduction increases. The maximum soot reduction affect was seen at locations in closer proximity to plasma discharge compared to locations far away from plasma discharge.