In the face of the growing energy crisis and environmental challenges, substantial efforts are now directed toward sustainable clean energy as a replacement for traditional fossil fuels. CO2 photoreduction into value-added chemicals and fuels is widely recognized as a promising approach to mitigate current energy and environmental concerns. Photocatalysts comprising single atoms (SAs) supported on two-dimensional (2D) semiconducting materials (SAs-2DSemi) have emerged as a novel frontier due to the combined merits of SA catalysts and 2D materials. In this study, we review advancements in metal SAs confined on 2DSemi substrates, categorized into four groups: (1) metal oxide-based, (2) g-C3N4-based, (3) emerging, and (4) hybridized 2DSemi, for photocatalytic CO2 conversion over the past few years. With a particular focus on highlighting the distinct advantages of SAs-2DSemi, we delve into the synthesis of state-of-the-art catalysts, their catalytic performances, and mechanistic elucidation facilitated by experimental characterizations and theoretical calculations. Following this, we outline the challenges in this field and offer perspectives on harnessing the potential of SAs-2DSemi as promising photocatalysts. This comprehensive review aims to provide valuable insights for the future development of 2D photocatalytic materials involving SAs for CO2 reduction.