Abstract: Green diesel is a second-generation biofuel developed in response to the increasing demand for liquid fuel and the predicted decrease in the availability of fossil fuels, especially diesel as the main liquid fuel used in transportation vehicles. Green diesel can be produced via deoxygenation from various feedstocks, such as vegetable oils, animal fats, fatty acids, and waste cooking oils. Normally, the deoxygenation reaction in green diesel production occurs in a multiphase system. There are three main pathways in the liquid phase of the reaction: decarboxylation, decarbonylation, and hydrodeoxygenation, from which liquid alkane hydrocarbons can be derived, and these are known as green diesel. This review paper discusses several deoxygenation pathways in a multiphase-reaction process to produce green diesel. Nickel metal is a non-noble metal catalyst which has been confirmed from many studies for use in deoxygenation with good performance. The performance of the nickel catalyst depends on different factors including the type of catalyst support and promoter, reaction temperature, reaction pressure, and reaction time. Finally, recent progress and future trends in green diesel production are discussed.