The workplace has thus far been neglected within the ever-expanding literature on the effect of ethnic diversity in social contexts on generalized social trust. Nevertheless, in the workplace individuals are continuously exposed to people of different ethnic background, which makes it a highly fruitful setting for examining various theories of the role of interethnic contact and exposure to ethnic diversity on social trust. In this paper we analyze the effect of workplace diversity on trust by merging the first five rounds of the European Social Survey with elaborate administrative data from public registers on workplaces in Denmark. Consistent with theories positing negative effects of interethnic exposure, we find a negative effect of ethnic diversity in the workplace on social trust. Additional analyses show that the effect of diversity in the workplace is independent from that of the residential setting, thus establishing workplace diversity as an independent influence on trust. Furthermore, the negative association between workplace diversity and social trust is confirmed in analyses based on panel data (generated through a follow-up survey of some of the original ESS respondents) with individual-level fixed effects, which further strengthen our causal interpretation of the relationship.