Organizational justice has been shown to play an important role in employees' affective and performance outcomes particularly in uncertain contexts. In this study, we investigated the interaction effect of job insecurity and organizational justice on employees' performance, and examined the mediating role of work engagement from the perspective of uncertainty management theory. We used 2-wave data (Study 1) from a sample of 140 Chinese employees and 3-wave data (Study 2) from a sample of 125 Chinese employees to test our hypotheses. In Study 1, we found that when employees perceived low levels of organizational justice, job insecurity was significantly negatively related to job performance. In contrast, we found that job insecurity was not related to job performance when there were high levels of organizational justice. Study 2 again supported the interaction of job insecurity and organizational justice on job performance. Furthermore, it was found that work engagement mediated the interaction effect. The results of the mediated moderation analysis revealed that job insecurity was negatively associated with job performance through work engagement when organizational justice was low.