There is increasing awareness of the importance of providing mental health services and support that promote a recovery-oriented and human rights-based approach. A mental health service system that is guided by a rehabilitation and recovery perspective places emphasis on treating the consequences of the illness rather than just the illness per se, and on empowering people to regain control of their identity and life, and to have hope for the future. Within this philosophy, mental health policies in several countries advocate for the introduction of peer workers in mental health services, people with lived experience of mental health issues and recovery, who are employed to use their lived experience to support those who access mental health services. However, more effectiveness and implementation research is needed. Evidence also suggests that the period following hospital discharge is of high risk of treatment dropout for people with serious mental illness, thus interrupting their recovery process. Therefore, this vulnerable population may particularly benefit from more targeted interventions during this transitional period. The research project will conduct a pilot randomized controlled trial to evaluate the feasibility, implementation and potential effectiveness of the Critical Time Intervention-Peer Support model, a recovery-oriented based model for people with serious mental illness discharged from inpatient psychiatric treatment facilities in Portugal. The randomized controlled trial (RCT) will be conducted in three psychiatric services in the Lisbon Metropolitan Area and their catchment areas. People with diagnoses of psychotic disorders discharged from inpatient psychiatric treatment facilities will be recruited and randomly divided into CTI-PS intervention or usual care. Those allocated to the intervention group will additionally receive CTI-PS rather than usual care alone over a 9-month period. Outcomes at baseline, 9- and 18-months will be analyzed by multilevel models, considering the observations clustered within sites. Longitudinal analyses will be used to examine trends over time of the outcomes of interest. The implementation of the CTI-PS model will introduce a novel approach to community mental health care that has not yet been tried in Portugal. This study aims to explore to what extent this intervention can be effectively implemented in countries with the characteristics of Portugal. Additionally, the proposed research aims to contribute to the global knowledge about peer interventions by exploring whether the CTI model can maintain its effectiveness using peers.