Purpose: A systematic look at the effect of pre-operative BMI on post-surgical outcome in CD patients has not been performed. The Purpose of our study was to identify an independent effect of BMI on outcome of surgical intervention in CD. Methods: A single-center, retrospective study. We collected information on those 90 CD patients who underwent surgical intervention for a CD related complication between 2000 and 2009 and in whom, data on pre-operative BMI and post-surgical outcome was available. Patients were divided into following three groups according to their BMI at time of surgery: 18.5-24.9 mg/ kg2 (normal weight), 25.0-29.9mg/kg2 (overweight), equal to or > 30mg/kg2 (obese). Logistic regression analysis was performed to determine the relationship between BMI at the time of surgery and the post-operative outcome while on standard treatment. Poor outcome was defined as a complication, serious enough to require a non-standard intervention at the time of post-operative surgical follow-up appointment with the operating team. Subsequently, multivariable logistic regression analyses models were used to identify strongest predictors of outcome. The level of significance was assessed at p < 0.05. Results: 36, 18 and 36 CD patients were normal weight, overweight and obese respectively. Bivariate logistic regression analysis looking at the effect of BMI on surgical outcome of CD surgery revealed that obese patients were 2.21 times more likely to have a poor outcome after surgery when compared to normal weight patients and this reached statistical significance (P=0.025 OR 2.21) whereas, when overweight patients were compared to normal weight patients, their difference in terms of surgical outcome was not statistically significant (P=0.12 OR=0.63). During multivariable analysis, when we looked at the effect of other pre-operative variables which included type of surgery, patients' age at time of surgery, ethnicity and gender, history of smoking, age at diagnosis, number of years with CD, immunomodulator or steroid use, clinical disease activity and endoscopic disease activity while controlling for BMI; we found that only active endoscopic disease prior to surgery was associated with a statistically significant poor surgical outcome (P=0.036 OR 3.47 95%CI 1.08-11.10). Conclusion: BMI does play a role in predicting outcome of surgical intervention in CD. Patients with CD, who are obese at the time of a surgical intervention, are more likely to have a negative post-operative outcome when compared to patients with CD who are of normal weight at the time of surgery. Active endoscopic disease at the time of surgical intervention in patients with CD has a strong association with a negative post-surgical outcome.