Background: Physical comorbidities are the most common causes of early mortality among patients with mental disorders. Prevention and early treatment of physical comorbidities would lead to better outcomes. Hence, the aim to the study was to estimate the prevalence of physical health disorders present as comorbidities among long-term stay psychiatric inpatients and to compare the difference in the physical comorbidities among male and female patients. Materials and Methods: The study was conducted at Institute of Mental Health, Madras Medical College, Chennai. It was a descriptive study combining data from clinical files and nursing records related to the physical health of the long-term inpatients. The clinical records of long-term inpatients, defined as the duration of stay in the care facility for more than 5 continuous years between 1stJanuary and 30thJune, 2019 were assessed. Results: The estimated prevalence was74.2% (95% CI: 69.5-78.6) for at least one physical disorder comorbidity and 38.8% (95% CI: 33.8-43.9) had more than one physical comorbidities. Female in-patients have 2.7 times higher risk than males to have diabetes mellitus, hypertension and thyroid disorders. They also have 0.92 times higher risk than males to have anaemia. Conclusion: There is a high prevalence of physical comorbidities among long term psychiatric inpatients. Systems for the early detection and better clinical management of these physical comorbidities are essential in any long-term psychiatric facility.