Photocatalytic reduction of CO₂ is known as one of the most promising methods to produce valuable fuels and value-added compounds. To overcome selectivity and efficiency downsides, various photocatalysts have been designed and developed. This review discusses the state-of-the-art in photo-conversion of CO₂ over graphitic carbon nitride (g-C₃N₄)-based composites. The modification strategies to improve photocatalytic activity of g-C₃N₄ were classified into different categories and discussed as structural modifications, elemental doping, copolymerization, fabricating heterojunctions between g-C₃N₄ and other semiconductors, Z-scheme heterojunctions, noble metal/g-C₃N₄ photocatalysts, and design of ternary nanocomposites based on g-C₃N₄. Finally, perspectives and future research works in this field were also outlined.