Due to the world's increasing demand for energy and high reliance on fossil fuels to produce it, there has been an urgent need to explore alternative ways to produce cleaner energy. Green diesel produced from renewable resources, such as waste vegetable oil, is a promising alternative due to its compatibility with petroleum diesel produced from fossil fuels. This study investigated the simulation of the hydrotreatment process of waste vegetable oil (WVO) to produce green diesel. ChemCAD version 8 was used to develop the simulation, and a kinetic model based on the Langmuir–Hinshelwood mechanism (an LH-C-ND model) was developed, where fatty acids such as oleic, stearic, and palmitic acid in WVO are converted into long-chain hydrocarbons (C15, C16, C17, and C18). The effect of the process parameters on the green diesel yield was assessed at different temperatures, pressures, and H2/oil ratios. The optimal conditions for green diesel production were identified as a temperature of 275°C and a pressure of 30 bar, with an H₂/oil ratio of 0.33. Optimisation efforts focused on minimising the formation of CO₂, CO, and water. In these operating conditions, a high green diesel yield was achieved, with the conversion of WVO exceeding 90%, and over 80% of the products were useful for green diesel. This study contributes to Sustainable Development Goal (SDG) 7, which aims to ensure access to affordable, reliable, sustainable, and modern energy for all by exploring the production of cleaner energy alternatives like green diesel from waste vegetable oil. It is recommended to recycle unreacted hydrogen to increase the efficiency and lower operational costs, as well as to conduct a life cycle assessment to evaluate the overall environmental impact.