The need for renewable energy sources is increasing day by day to overcome the risk of depleting fossil fuel resources and the increase in greenhouse gas emissions. Fuel produced from renewable resources such as green diesel can be an alternative. In this study, a trickle bed reactor was used to hydrodeoxygenate triolein which is one of the main compounds of vegetable oil for green diesel production using NiMo/Al2O3 catalyst. The temperature range at which the reactions occurred was 290 °C, 310 °C, and 330 °C, while the hydrogen gas pressure range at which the reactions occurred was 5, 10, and 15 bar with H2 gas flow at a rate of 1 SLPM and liquid feed with a 3 mL/min flow rate. This study investigated the significance of the parameters on the conversion, yield, purity, selectivity, and hydrodeoxygenation of green diesel. The Response Surface Method (RSM) was utilized to predict the input parameters offering the optimum combination for green diesel yield. The optimum results were obtained at the highest H2 pressure of 15 bar and the highest temperature of 330 °C, with the following results: 99.96% of conversion, 76.43% of yield, 78.76% of purity, 92.93% of selectivity, and 68.23% of hydrodeoxygenation. © 2025 Informa UK Limited, trading as Taylor & Francis Group.