The aim is to correlate the relationship between body mass index (BMI) and dental caries in patients attending Baqai Dental College, Karachi, Pakistan. Materials and Methods: This cross-sectional study was conducted in the Department of Operative Dentistry, Baqai Dental College, between June 1 st , 2014 and March 1 st , 2015. A simple random technique was employed and 200 adult patients, aged 18-35 years were selected to participate in the study. A structured questionnaire was designed to gather information on age; gender; address; weight; height; decayed, missing, filled teeth (DMFT) index. Dental caries was examined using DMFT index and height and weight measured using BMI. P value is 0.05. Data were analyzed for descriptive statistics and Chi-square test was done to assess the relationship between BMI and dental caries using SPSS version 21. Results: The study shows significant correlation between BMI and DMFT scores, DMFT scores found more in obese/overweight patients. Conclusion: This study results showed a positive correlation between dental caries and BMI. Obesity is thought to be a predictor of dental caries so modification in diet and changes in lifestyle including physical exercises with dental examination and educational care is required.