Carbon dioxide (CO₂) assisted pyrolysis has emerged as a promising thermochemical strategy for converting biomass and waste feedstocks into value added products, especially syngas rich in carbon monoxide (CO). Unlike conventional inert atmospheres, CO₂ influences both product distributions and reaction pathways by participating in heterogeneous and homogeneous reactions that alter carbon conversion dynamics. This review synthesizes the latest advancements in CO₂ assisted pyrolytic systems with a particular focus on the mechanisms of CO formation and subsequent transformations, examining how CO₂ interacts with volatiles, char surfaces, and catalysts to promote CO yields and modify overall product quality. Critical aspects including CO₂ role as a mild oxidant, its synergistic effects with catalysts, mechanistic pathways such as Boudouard and reverse water gas shift reactions, and implications for industrial applications are comprehensively reviewed. Finally, knowledge gaps and future research needs for optimizing CO₂ assisted pyrolysis and enhancing CO production are identified.