["Corporate Social Responsibility and Environmental Management, EarlyView. ", "\nABSTRACT\nWhile the influence of market‐supporting institutions on firm behavior is well established in the literature, our understanding of institutional change dynamics—particularly the speed of pro‐market reforms—on corporate nonmarket strategies, such as ESG (Environmental, Social, and Governance) engagement, remains limited. To address this research gap, we develop a theoretical framework that investigates whether, how, and under what conditions the speed of pro‐market reforms creates constraints for firms engaging in ESG activities. Employing a dynamic institution‐based view and analyzing a panel data of Chinese publicly listed firms, we find that firms operating in regions undergoing rapid pro‐market reforms participate less actively in ESG initiatives. Critically, CEO characteristics act as buffers: corporate leaders with international experience and/or hometown ties appear to mitigate reform‐induced uncertainty, enabling more resilient ESG navigation during institutional transitions. These findings advance the dynamic institutional perspective by demonstrating how temporal institutional shifts shape corporate behavior.\n"]