Unaccompanied refugee minors (URM) are the most vulnerable group of refugees suffering from higher levels of mental health problems. Yet, there is also a group of URM with little or no symptoms or disorders. A major predictor for positive mental health outcomes is the social support network in the post-flight period which has rarely been investigated for the group of URM. The present study analyzes differences between perceived social support from family, peers, and adult mentors in URM, with subgroup analyses of peer and mentor support in URM with and without family contact. Furthermore, we investigate whether social support from each of the three sectors moderates the relationship between stressful life events (SLE) and mental health of URM with family contact. Questionnaire data were collected from 105 male URM from Syria and Afghanistan aged 14–19 years who were living in group homes of the Child Protection Services in Leipzig, Germany, in summer 2017. URM receive most social support from their families, followed by peers and adult mentors. URM without family contact received less peer and mentor support compared to URM with family contact. Lower social support from mentors increased the risk for PTSD, depression and anxiety symptoms after SLE, whereas lower social support from peers increased the association between SLE and anxiety symptoms. Mentor and peer support in the host country is relevant for the processing of SLE. URM without family contact represent a “double burden” group, as they might feel less supported by other social networks.