The prevalence of psychological distress and its association with ethnic discrimination was examined among 13,703 participants (36 to 79 years of age) in a population-based study of health and living conditions in areas with indigenous Sami, Kven (descendants of Finnish immigrants), and Ethnic Norwegian populations (the SAMINOR study). Sami and Kven males reported greater levels of stress than Ethnic Norwegians. Ethnic discrimination was strongly associated with elevated levels of psychological distress. Results suggest that ethnic discrimination is a major potential risk factor for poor mental health, and may contribute to ethnicity-related differences in mental health between Sami and non-Sami populations.