Idiosyncratic deals (i-deals) are widespread in organizations, but their relationship to employees’ work stress has been unclear. Based on the model of effort-reward imbalance (ERI), our study investigates this relationship and takes into account the role of social comparisons and denied i-deals. Two types of i-deals, flexibility i-deals and development i-deals, have been studied. We applied a time-lagged research design for which we collected data from 120 employees at two points in time to test our hypotheses. The results show that development i-deals significantly reduce employees’ ERI, whereas flexibility i-deals do not relate to employees’ ERI. Above that, the denial of i-deals increases ERI. Our results also show that social comparisons with co-workers’ i-deals can influence the relationship between an employee’s i-deals and his or her ERI. Hence, this study demonstrates that i-deals can affect employees’ ERI, which may have diverse health-related and job-related consequences.