【Abstract】 Firms tend to seek optimal distinctiveness when choosing CSR engagement timing. Building on the perspectives of optimal distinctiveness and competitive dynamics, this paper explains why firms' CSR engagement timing toward a certain event is affected by dynamic competitive effects. That is, to achieve optimal distinctiveness, focal firms pay more attention to their main competitors that are similar in market, size and resources. We apply a discrete-time survival analysis of 869 Chinese listed firms' CSR engagement action toward the COVID-19 pandemic during the first half of 2020. The results support the mechanism that when a highly similar competitor engages in CSR activities, it raises the probability that the focal firm engages itself beyond levels based solely on its own characteristics and common time-dependent factors.