Objective: To determine the association of body mass index with various primary headache disorders. Method: The ambispective study was conducted at the Department of Medicine, Shalamar Institute of Health Sciences, Lahore, Pakistan, from January 2020 to March 2021, and comprised data of patients who presented to outpatient departments of Neurology and Medicine with complaint of recurrent or persistent headaches. Body mass index of each subject at the time of latest headache visit was recorded. A control group of 200 individuals was also raised and the body mass index of its subjects was measured. Headache disorders were classified as per International Classification of Headache Disorders-3 beta criteria. Correlation of frequency of different types of primary headaches with body mass index was explored. Data was analysed using SPSS 20. Results: Of the 400 subjects, 200(50%) each were cases and controls. There were 132(33%) males and 268(67%) females. The overall mean age was 37.4+/-14.7 years and mean body mass index was 27.3+/-5.87kg/m2. Migraine was found in 183(46%) subjects compared to tension-type headache 96(24%). Migraine was more common in subjects with high body mass index (p<0.05). Conclusion: Primary headaches constitute a significant health problem. Among various risk factors weight-gain is one that can predispose an individual to increased frequency of migraine. Key Words: Primary headache disorders, Migraine, Tension type headache, Body mass index.