Psychological contract (PC) describes the labor relationships through the different promises made by the employer towards the employees and the promises made by employees to their employer. PC mutuality is defined as the agreement about whether these promises were actually made. Mutuality is a key element in PC theory. The aim of this study is to test a mediation model of relationships between PC mutuality and work related outcomes, through PC fulfillment. We analyze whether PC mutuality regarding promises made by the employer are significantly related to employees’ affective, attitudinal, and behavioral work-related outcomes, and whether fulfillment of PC promises mediates these relationships. The sample was composed of 942 employees and their HR managers from 47 organizations in three sectors (food, education, and sales). Mediation model is tested, using the bootstrapping technique developed by Hayes (2009). The study provides support for the hypothesized mediation model. Results show that PC mutuality predicts work-related outcomes such as job satisfaction, well-being, organizational commitment, intention to quit, in-role perceived performance, and perceptions of PC violation, and that PC fulfillment partially mediates these relationships. These findings provide theoretical insights into PC theory, highlighting the relevance of PC mutuality. They offer practical suggestions for companies about the importance of achieving mutuality in their relationships with employees in order to increase positive work-related outcomes.