Purpose: People with severe mental illness (SMI) experience poor physical health and premature mortality, contributed significantly by modifiable lifestyle risk factors such as poor nutrition, low cardiorespiratory fitness, and physical inactivity. Lifestyle interventions can reduce cardiometabolic risk and confer a range of other positive mental and physical health benefits. We assessed the feasibility, acceptability, safety, and preliminary effectiveness of a lifestyle (combined dietary and exercise) intervention lead by senior exercise and dietetics students in a residential mental health rehabilitation setting. Design: Single arm, prospective study evaluating outcomes pre and post a 10-week dietary and exercise intervention. Method: People with SMI from three residential rehabilitation units participated in a mixed aerobic and resistance training exercise intervention three times per week that was combined with a dietary intervention (six individual and group sessions). Primary outcome considerations were feasibility (recruitment, retention, and participation rates), acceptability, and adverse events. Secondary outcomes were preliminary effectiveness; (functional exercise capacity, volume of exercise, and metabolic markers), psychiatric symptoms, quality of life, and attitudes to exercise. Results: Forty-two participants were recruited (92% primary diagnosis of schizophrenia). Intervention feasibility was supported by high levels of recruitment (68%), retention (77%),