Patients with serious mental illness have an increased prevalence of the metabolic syndrome in comparison to the general population. Metabolic syndrome is a constellation of cardiovascular risk factors including diabetes, hypertension, obesity and dyslipidemia. It is potentially reversible and may explain the higher incidence of cardiovascular disease in patients with serious mental illness. The aim of the study is to see the prevalence of metabolic syndrome among mentally ill patients and what might be the underlying the cause behind the scene A descriptive, retrospective study was conducted at mental health clinic, Batticaloa, Teaching Hospital (BTH), Sri Lanka. The data were collected over a period of two months from 15th of October to 15th of December 2017. Data were harvested from the medical records. Total 55 mentally ill patient's medical records were analyzed for this study. Out of 55, females were 30 (54.5%) and males were 25 (45.5%). Furthermore, 30 (54.5%) patients had an evidence of metabolic syndrome. The association of metabolic syndrome among male and female was not statistically significant (P > 0.05). In this study, metabolic syndrome is more prevalent among, patient with trifluoperazine (70%) drug group, risperidone (66.6%) and olanzapine (53.12%).