The higher consumption of diesel oil have caused the scarcity of petroleum and increasing its cost. The efforts have been performed to develop alternative fuels especially, to the diesel oil for fully or partial replacement. Biodiesel has environmental benefits due to the neat or blends biodiesel can reduce carbon monoxide (CO) emissions, hydrocarbons (HC), particulate matter (PM), and increase nitrogen oxides (NOx) emissions compared with diesel fuel used in an unmodified diesel engine. Here we have used waste fish oil as the raw material for production of biodiesel. Biodiesel has been prepared by the process called transesterification. The blends of this biodiesel was made with pure diesel and had been tested in the single cylinder four stroke engine to find out various parameters. From the data obtained the biodiesel blends shows better fuel properties than the pure diesel.