In this study investigated both experimentally and numerically in detail the combustion characteristics of a diesel engine operating with biodiesel fuel produced from fig seed oil at full load and different speeds. 5%, 10% and 20% biodiesel blended fuels added to diesel fuel, and these blends were compared with diesel fuel. AVL Fire software was used in numerical study. The results showed that it was confirmed that the numerical model is consistent. Heat release rate, p-V diagram, charge change process, mass fraction burned, cyclic differences, burning duration, turbulence velocity distribution and mixture formation were evaluated. Experimental results showed that when biodiesel fuel blends were used, the in-cylinder pressure and heat release rate increased. In addition, the pumping loss was slightly improved. Maximum heat release rates of diesel, 5%, 10% and 20% biodiesel blended are 30.17, 32.2, 35.25 and 34.23, respectively at 2000 rpm. It can be said that with the biodiesel mixture, faster burning and more fuel burned. Mass fraction burned of diesel, 5%, 10% and 20% biodiesel blended are 0.32%, 0.51%, 1.04%, and 0.78%, respectively at 2000 rpm and TDC. As a result, B10 fuel increases the combustion quality and this ratio can be used as an alternative fuel.