Background: Worldwide, breast cancer is most common cancer among women. In India and other developing countries, breast carcinoma ranks second only to cervical carcinoma among women. Although studies have been done globally, to find association between BMI and breast cancer, very few studies in India document any such association. Purpose: To find out the association between BMI and breast cancer. Materials and Methods: A Case-control study was done from August 2009 - July 2010 in the wards of General Surgery and Oncosurgery at Pt.B.D.Sharma, PGIMS Rohtak, Haryana. A total of 128 histopathologically confirmed new cases of breast cancer during the study period were taken as cases. Equal number of controls was selected by simple random sampling. Controls were matched for age with range of ±2 years. Subjects were interviewed using a pretested questionnaire after obtaining written informed consent. Data were analyzed by applying appropriate statistical tests using SPSS version 17. Results: Age group of the cases was 25 - 78 years, while that of the controls was 24 - 79 years. Proportion of cases and controls living in rural areas were more than those living in urban areas. A significant association of breast cancer cases was found with high BMI and high fat intake Conclusion: Obesity and high fat intake are the significant risk factors, which are modifiable. So women should be encouraged to take care of all these factors. Maximum cases presented in late stages so public awareness of this fatal disease must be developed.