Background Improving care for patients with severe mental illness in Latin America requires effective strategies that are low-cost. One such strategy is a volunteering scheme, referred to as befriending, which seeks to support the social integration of patients. Despite positive reports in other world regions, this intervention has not been studied in Latin America. Whilst befriending programmes commonly form patient-volunteer dyads, group arrangements may be an alternative with some benefits. Here, we aim to explore the feasibility, experiences and outcomes of a group volunteer befriending intervention for patients with severe mental illness in Colombia. Methods In this exploratory non-controlled study, 10 groups of five individuals were formed, each consisting of three individuals with schizophrenia or bipolar disorder and two volunteers from the community in Bogotá, Colombia. Each group was encouraged to participate together in social activities within their community over a 6-month period. Patients’ quality of life, objective social outcomes, symptom levels and internalised stigma were assessed before and after the intervention. Patients’ and volunteers’ experiences were explored in semi-structured interviews which were analysed using inductive content analysis. Results Outcomes were available for 23 patients. Whilst their objective social situation had significantly improved at the end of the intervention, other outcomes did not show statistically significant differences. The interviews with participants revealed positive experiences which fell into five categories: 1) stigma reduction; 2) personal growth; 3) formation of relationships; 4) continuity and sustainability of befriending; 5) acceptability and feasibility of befriending. Conclusions A volunteer befriending programme in small groups of two volunteers and three patients is feasible and associated with positive experiences of participants. Such programmes may also improve the objective social situation of patients. This low-cost intervention may be useful for patients with severe mental illnesses in Latin America. Trial registration ISRCTN72241383 (Date of Registration: 04/03/2019, retrospectively registered).