This work involves a study of the effect of blending of commercially available petrodiesel with biodiesels derived from NaOH-catalyzed homogeneous transesterification of methanol with groundnut and soybean oils, respectively. Some basic properties (density, kinematic viscosity, flash point and heating value) of the purchased petrodiesel, pure groundnut and soybean biodiesels, as well as formulated blends of the biodiesels with petrodiesel were measured using standard literature procedures. The density, kinematic viscosity and flash point of petrodiesel/biodiesel blends increases with increase in the concentration of biodiesels in the blends. Blending is more important for the improvement of the quality of groundnut oil biodiesel than for soybean oil biodiesel. The heating value of petrodiesel/biodiesel blends increases with decrease in the blend levels.