Physical health problems and unhealthy lifestyle behaviours are common in people with severe mental illness (SMI), leading to high levels of mortality.There is some evidence that nurse-led interventions involving comprehensive health checks may be effective in improving physical health in people with SMI. This quasi-experimental before-and-after study investigated the impacts of the Thai Health Improvement Profile (HIP-T) on the physical health and health behaviours of people with schizophrenia over 1-year. All 105 service-users who volunteered to participate completed the study. There were significant reductions in mean BMI (−0.78 kg/m2, P <.001) and bodyweight (−1.13 kg, P <.001) at post-test. There was also a significant decrease in the total number of “red-flagged” HIP-T items, suggesting lowered potential health risks (P <.001). Overall, 23 patients (22%) were found to have moved to a healthier BMI classification after 1-year. The findings suggest that the HIP-T intervention has potential for improving the physical health of people with SMI when integrated into routine community mental health care.