Objective This study examined whether having peer specialists (PS) in psychiatric multidisciplinary outreach teams was associated with a lower risk of hospitalisation, improved social functioning and decreased problem behaviours. Design and setting This study was a retrospective cohort study based on medical records. This study was conducted as a part of the Japanese Outreach Model Project 2011-2014, which provides services for persons diagnosed mainly as ICD-10 F0, F2 and F3, who have a high possibility of hospital admission/readmission with regular Japanese outpatient care. Participants A total of 292 participants (clients) from 31 multidisciplinary outreach teams with and without PS (n=108 and 184, respectively) fulfilled the inclusion criteria and were included in the analysis. Outcome measures The primary outcome measure was hospitalisation during follow-up. The difference in hospitalisation during the follow-up between teams with and without PS was analysed by Kaplan-Meier survival curves and a Cox proportional hazards model. The secondary outcome measures were social functioning (Global Assessment of Functioning, GAF) and problem behaviours (Social Behaviour Schedule, SBS) of clients, and were assessed at baseline and at 6-month follow-up. Changes in social functioning and problem behaviours were compared between clients cared for by the two team types. Amount and content of the service were also compared. Results The clients cared by teams with PS had a significantly decreased probability of hospitalisation in Cox proportional hazards models adjusting for baseline characteristics (HR=0.53, 95% CI 0.31 to 0.89). The 6-month change in GAF or SBS was not significantly different between the two groups. Conclusion This is an observational study in which the presence of a PS appeared to be associated with a reduced rate of hospitalisation. A randomised study would be required to demonstrate a causal relationship.