Biochar is a solid residual produced from the thermochemical conversion of lignocellulosic biomass via pyrolysis or gasification. It is abundantly available and has a unique structure as well as multiple functionalities. This makes biochar a potential candidate for use as a catalyst or support in catalytic reactions relating to biomass conversion such as catalytic pyrolysis, gasification, esterification of bio-oil, tar reforming, hydrothermal treatments and upgrading of bio-oil. Although numerous studies have been conducted on the potential use of biochar in various catalysis reactions, information on the overall overview and evaluation of the feasibilities of its use, especially in biomass-related conversions, is still limited. This study reviews the state-of-the-art for the production of biochar catalyst as well as its application as a catalyst or support for catalysts in producing biofuel or syngas from biomass. Special attention is given to the reaction pathway of reactants over the surface of biochar and the potential application of biochar in commercial applications. The prospects and challenges for the application of biochar as catalysts for the thermal conversion of biomass are also proposed.