Biodiesel fuel is a potential alternative energy source for diesel engines due to its physiochemical characteristics relatively similar to those of traditional diesel fuel. In this study, the performance, emission, and combustion features of a mono cylinder DI diesel engine are assessed using 20% Pumpkin seed methyl ester (PSOME20) and considering varying injection pressures (200, 220, 240, and 260 bar). The considered Pumpkin seed oil is converted into pumpkin biodiesel by transesterification and then used as fuel. The findings demonstrate that the Brake Thermal Efficiency (BTE) of PSOME20 can be raised by 1.68%, and the carbon monoxide (CO), hydrocarbon (HC), and smoke emanations can be lowered, while oxides of nitrogen (NOx) emissions are increased at an injection pressure (IP) of 240 bar compared to the standard IP of 200 bar. The cylinder pressure and the Heat Release Rate (HRR) become higher at 240 bar, whereas the ignition delay is shortened with respect to PSOME20 at a normal IP of 200 bar. © 2022 Elsevier B.V., All rights reserved.