Objective For the first time, a health insurance fund's Social Service (SD) module was implemented in a German child and adolescent psychiatry model project (MP) to support relatives. The SD collaborates with the Case Management (CM) of the MP. The study investigated: 1) SD-CM collaboration barriers and facilitators, 2) legal guardians' (LG) perception of the SD, and 3) the perceived benefit of SD counseling. Methods A focus group with n = 7 SD and CM staff and qualitative interviews with n = 15 LG were content-analyzed. Results Barriers and facilitators of SD-CM-collaboration were mapped across the categories structural characteristics, professional role, personal characteristics and LG' reactions. Some LG lacked a conception of the SD and requested more information. The SD provided emotional and administrative support for LG and mediated access to further services. Conclusion Recommendations are derived for the MP.