The mental health of refugees is influenced by a variety of pre-, peri- and postmigratory factors. It remains largely unclear how social determinants influence the utilization of psychiatric-psychotherapeutic treatment. We applied a questionnaire survey to 189 refugees from a clinical sample in a psychiatric hospital and from a control sample, which was not in treatment. The influence of social factors on psychopathology and utilization of care was analyzed by means of a CHAID algorithm. The total sample was highly stressed (54% PTSD and 41.4% depression symptoms). Patients were more severely affected in all psychometric scales as well as in traumatization and they were less able to draw on resources such as a social network or residence permit. The strongest predictor for psychotherapeutic-psychiatric treatment was social isolation in the living environment. For patients, the lack of a work permit was the strongest predictor of depression symptoms. The results point to the importance of postmigratory social determinants for the mental health of refugees. In particular, stable social relationships, together with formal factors such as work permit and residence title, should help to reduce mental distress and the need for psychiatric treatment.