Objective: To gain insight into the complex relationship between job insecurity and in-role and extra-role performance. Autonomous work motivation is investigated as a mediator in this relationship. The quality of the employee-supervisor relationship (LMX) is investigated as a moderator between job insecurity and autonomous work motivation. Methods: Cross-sectional data were collected by online surveys among 206 Dutch and Belgian employees. Multiple regression analyses were performed to test the hypotheses. Results: Job insecurity was negatively associated with both in-role and extra-role performance. Autonomous work motivation mediated the negative relationship between job insecurity and in-role and extra-role performance. LMX did not moderate the negative relationship between job insecurity and autonomous work motivation. Conclusions: Organizations need to prevent job insecurity and limit the negative consequences of job insecurity for sustaining employees' autonomous work motivation and job performance.