In this report diesel combustion and exhaust emission with neat diesel fuel and diesel-biodiesel blends is investigated. In the investigation, first, the making of biodiesel is done by esterification and second, experiment is conducted with neat diesel fuel and diesel-biodiesel blends in a four stroke naturally aspirated (NA) direct injection (DI) diesel engine. The volumetric blending ratios of biodiesel with conventional diesel fuel are set at 0, 5, 10, 15, and 20. Compared with neat diesel fuel, diesel-biodiesel blends show lower carbon monoxide (CO), and smoke emissions due to the improved properties after esterification and the presence of oxygen in the biodiesel. With diesel-biodiesel blends nitrogen oxide (NOx) is reduced at retarded injection timing but increased at advanced injection timing. Engine noise is reduced significantly with all diesel-biodiesel blends.