The individualization of working conditions has culminated in the form of “i-deals,” which are uniquely negotiated arrangements between employees (i-dealers) and their supervisor. Implementing such idiosyncratic deals, however, only makes sense when their benefits outweigh their costs. To assess their merit, co-worker reactions should be considered. Do i-deals trigger fairness perceptions and emotions among co-workers? And how do these factors influence co-workers’ behaviors? To date, the cognitive and emotional mechanisms of co-workers’ behavioral reactions have been underdeveloped. In this article, we build on social comparison theory to develop a process model. We argue that social comparison is not a given, as co-workers might not necessarily compare themselves with the i-dealer. Yet, if they engage in comparison, this can be upward when they feel disadvantaged or, alternatively, downward. Such comparisons include a unique set of emotions and fairness perceptions, which together influence co-workers’ behaviors positively or negatively. Moreover, we argue that the boundary conditions of the relational context within which i-deals unfold play an important role. Our model offers theoretical insights into co-worker reactions to i-deals as well as a future research agenda. The model also aids practitioners in understanding co-workers’ reactions and in guiding them to assure positive reactions.