<p>This study examines how job insecurity, a crucial job characteristic in rapidly changing employment contexts, influences employees’ pro-environmental behavior at work (PEBW). Drawing on the Conservation of Resources theory and Social Exchange theory, it proposes that job insecurity exerts an indirect impact on PEBW through employees’ affective commitment, with prosocial motivation acting as a moderating factor. Data were collected in three waves from 231 working adults in South Korea, enabling temporal separation of measures and reducing common method bias. Structural equation modeling and bootstrapping analyses revealed that job insecurity alone did not directly predict PEBW; rather, it weakened individuals’ affective commitment, which in turn lowered their willingness to engage in green actions. Furthermore, prosocial motivation emerged as a significant buffer, alleviating the detrimental effect of job insecurity on affective commitment. These results point to the critical role of employees’ emotional ties to the organization and personal altruistic orientations in shaping ecological behaviors amid perceived employment threats. By integrating multiple theoretical perspectives, the study offers a more holistic explanation of why some employees persist in their environmentally friendly efforts under precarious conditions while others do not. The findings suggest that organizations seeking to foster sustainable practices should carefully manage job insecurity perceptions, reinforce employees’ emotional connection to the firm, and nurture prosocial motivations. In so doing, firms may mitigate the negative impacts of workplace uncertainty on discretionary environmental engagement and support a more resilient and sustainable organizational culture.</p>