Recovery from work is a critical component for employees' proper functioning. While research has documented the beneficial effects of after-work recovery, it has focused far less on the recovery that happens while at work in the form of work breaks. In this review, we systematically review available empirical evidence on the relationship between work breaks and well-being and performance among knowledge workers. Doing so enables us to (a) integrate studies from multiple disciplines, (b) propose a conceptual framework for categorizing work breaks, and (c) provide a future research agenda for studying the role of work breaks in employee well-being and performance. Using Cochrane's guidelines, we review observational and intervention studies (N = 83). Based on the extant research, we propose that work breaks can be described and classified in terms of five features: initiator, duration, frequency, activities, and experiences. The result of our review is an integrative model that comprehensively captures the relationship between work breaks and well-being and performance outcomes, as well as the mechanisms and boundary conditions of these relationships. We conclude by proposing avenues for the future study and practice of work breaks.