Objective Peer support is playing an increasing role in the treatment of severely mentally ill people. International findings are available on its effectiveness. However, little is known about knowledge, use and benefit assessment in Germany. This paper addresses this question and presents results from an observational study with 10 participating clinics in southern Germany. Methods As part of the observational cross-sectional study with people with severe mental illness (IMPPETUS, N=359), sociodemographic and illness- and treatment-associated data were collected by trained study staff between March 2019 and September 2019. Binary logistic regression was used to analyse a possible association with peer support use. Results 38% (N=138) of respondents reported knowledge about the possibility of peer support; 15% (N=55) affirmed its use. Use of peer support varied across sites (between 6.5 and 37.5%) and was associated with household income. Significantly less frequent use of peer support was among those with high versus low household income (OR=0.20 [95% CI: 0.06-0.68], p=0.01). Of respondents with peer support use (N=55), 78% reported perceiving peer support to be helpful or highly helpful. Discussion Peer support not only proves to be effective under study conditions with regard to various outcomes, but is also assessed as beneficial under routine conditions in a defined care region by the majority of users. However, only a few respondents knew and used the possibility of peer support. Conclusion In order to implement peer support more strongly, information about this kind of service should be provided more effectively and a dialogue about successful implementation experiences should be initiated on a regional level.