OBJECTIVE: People with severe mental illness (SMI) have a reduced life expectancy, primarily due to chronic somatic diseases like cardiovascular disorders. Integrated care in general practice addressing mental and physical health may reduce excess mortality in this population. This review assessed the effectiveness of collaborative care, general integrated care, and physical health interventions in reducing overall mortality in patients with SMI. Secondary outcomes included disease-specific mortality, cardiovascular health indicators, and health-related quality of life. METHODS: We searched PubMed, PsycINFO, Cochrane Library, and Embase for randomized controlled trials published before April 24, 2024. Eligible studies focused on integrated care interventions targeting somatic health in patients with SMI. Two reviewers independently conducted data extraction and risk of bias assessment. The study was registered with PROSPERO (CRD42022328464). RESULTS: Of 2904 identified publications, 17 were included (covering 13 studies). Seven studies reported mortality data, with one showing reduced mortality in patients with major depressive disorder receiving collaborative care. No studies examined disease-specific mortality. Nine studies assessed cardiovascular outcomes, with three reporting reduced cardiovascular risk in collaborative care interventions simultaneously targeting depression and cardiovascular factors. Seven studies reported on quality of life, with three finding improvements. Study quality was rated moderate to high. CONCLUSION: We found low-certainty evidence that collaborative care reduces mortality in depression. There was moderate evidence that collaborative care models, simultaneously addressing mental and cardiovascular health could potentially improve cardiovascular health in depression. The limited number of studies and their focus on depression limit the generalizability of these findings to other SMIs.