People may be subjected to discrimination from a variety of sources in the workplace. In this study of mental health workers, we contrast four potential perpetrators of discrimination (managers, co-workers, patients, and visitors) to investigate whether the negative impact of discrimination on victims’ well-being will vary in strength depending on the relative power of the perpetrator. We further explore whether the negative impact of discrimination is at least partly explained by its effects on people’s sense of organizational justice, and whether (...) the strength of mediation varies according to the source of discrimination. Using survey data from 1,733 UK mental health workers, a structural equation model was designed to test these hypotheses following a bootstrap approach. Discrimination from all sources was related to well-being, with that from managers having the strongest effects. The results support an explanation of the effect of discrimination on well-being in terms of organizational justice perceptions for discrimination from managers and from visitors, but less so for discrimination from co-workers or from patients. The study highlights the importance of differentiating amongst sources of discrimination at work and the salience of organizational justice perceptions in explaining the effects of discrimination from some sources. (shrink)