The aim of the present study was to establish the feasibility of conducting a full-scale trial and to estimate the preliminary effect of a Chinese Health Improvement Profile (CHIP) intervention on self-reported physical well-being of people with severe mental illness (SMI). The study used a parallel-group, open-label, cluster-randomized, controlled trial (RCT) design. Twelve community psychiatric nurses (CPN) and their corresponding 137 patients with SMI were randomized into the CHIP or treatment-as-usual (TAU) groups. After training, the CPN completed the CHIP at baseline and 12 months, and the findings were used to devise an individualized care plan to promote health behaviour change. Patients were assessed at baseline and 6 and 12 months after starting the intervention. There was an observed positive trend of improvement on the physical component subscale of SF12v2 in the CHIP group compared to the TAU group after 12 months, but the difference did not reach statistical significance (P = 0.138). The mental component subscale showed a similar positive trend (P = 0.077). CHIP participants were more satisfied with their physical health care than TAU patients (P = 0.009), and the CPN were positive about the usefulness/acceptability of the intervention. There were significant within-group improvements in the total numbers of physical health risks, as indicated by the CHIP items (P = 0.005). The findings suggest that it is feasible to conduct a full-scale RCT of the CHIP in future. The CHIP is an intervention that can be used within routine CPN practice, and could result in small-modest improvements in the physical well-being of people with SMI.