In this study we extend the work of Brower, Lester, Korsgaard and Dineen (2009) on mutual trust by proposing and testing whether and how the interactive effects of trust in the supervisor and trust in the subordinate account for subordinates' task and contextual performance through the mediating role of psychological contract fulfillment. We tested our mediated moderation model on 182 supervisorÀsubordinate dyads of three service firms in Hong Kong. Results indicated that fulfillment of psychological contract fully mediated the effects of mutual trust between supervisors and subordinates on subordinates' task and contextual performance.Key points 1 We unveil the neglected blackbox of the relationship between psychological contract fulfillment and employees' work performance. 2 Fulfillment of psychological contract was found to fully mediate the effects of mutual trust between supervisors and subordinates on subordinates' task and contextual performance. 3 The building and maintaining of a mutual trustful relationship between a supervisor and his/her subordinate is salient to induce both of the parties to honor his/her part of work obligations, which in turn faciliates subordinates' work performance.Given the highly competitive global market, it is becoming increasing salient for business firms to realize the role of trust in maintaining group harmony and effectiveness. However, developing and maintaining trusting relations become a challenging issue when a