Abstract Background: Obesity is a well-known risk factor for breast cancer recurrence and poor prognosis. The objective of this study was to evaluate the effect of body mass index (BMI) on survival in breast cancer patients. Methods: We performed a retrospective analysis of 50 breast cancer patients treated in our hospital from January 2012 to December 2013. Patients were divided according to body mass index when diagnosed into: normal weight BMI 25 Kg/m2, over weight BMI ≥ 25 Kg/m2 to 30 Kg/m2, obesity BMI ≥ 30 Kg/m2. In this study the effect of body mass index on progression free survival (PFS) and overall survival (OS) was evaluated. Results: The disease free survival (DFS) and overall survival (OS) decreased in overweight and obese patients. Both overweight and obesity were predictors for increased risks of breast cancer relapse and mortality with a median disease free survival for overweight 29 mons and obese patients 11 mons and a median overall survival for overweight patients 49 mons and obese patients 39 mons. Conclusion: Obesity and overweight are associated with poorer disease free survival and overall survival in patients with breast cancer.