Interpretations of correlational research on the social origins of psychological well-being are limited by the possibility of reciprocal influences between persons and their social situations and by respondent bias. These issues are addressed in a study of the relation between the social environment at work and mental health. Two components of a social environment were measured: a common social environment, the social climate shared by employees in the same work setting. The study related (a) averaged co-workers' ratings and individuals' own ratings of the social environment to (b) individuals' self-reported psychological well-being. A group of 37 bank branches represented work environments, and nonmanagerial personnel in the branches served as participants. Results indicated that the quality of the social environment at work is related to the mental health of employees. More important, the relation was confirmed with an independent measure of the social environment. Aggregate co-worker ratings of the common social environment were significantly correlated with individual depression and anxiety. However, an individual's perceptions appeared to mediate the social environment's impact. As hypothesized, well-being was more closely tied to the proximal individual social environment than to the more distal common social environment.