The purpose of the present study was to determine the prevalence of diabetes and its effect on surgical outcomes in patients undergoing emergent, in-patient cholecystectomy for acute cholecystitis. Some 8.3 % of the U.S. population has diabetes and this number is projected to rise to 21-33 % by 2050. Diabetes is considered to be associated with a higher incidence of acute cholecystitis; however, its impact on outcomes is unknown. The American College of Surgeons National Surgical Quality Improvement Program database was queried to identify all patients with acute cholecystitis who underwent emergent in-patient cholecystectomy from 2004 to 2010. The study population was divided into two groups: diabetics and non-diabetics. Diabetics were further subdivided into those taking oral medication and those on insulin. Demographics, co-morbidities, and wound classification were compared with univariate analysis, and 30-day outcomes were compared with univariate and multivariate analyses. A total of 5,460 patients met the inclusion criteria. Of these 770 (14.10 %) had a diagnosis of diabetes. Mortality was higher for diabetics than for non-diabetics [4.4 vs 1.4 %, adjusted odds ratio (AOR) (95 % CI): 1.79 (1.09, 2.94), adj-p = 0.022]. Preoperative perforation rates were 25.1 and 13.0 %, respectively [AOR (95 % CI): 1.34 (1.09, 1.65), adj-p = 0.005]. The adjusted risk of cardiovascular events and renal failure was significantly higher for diabetics. Insulin treatment, but not oral medication, was associated with a significant increase in mortality, preoperative perforation, superficial surgical site infection, septic shock, cardiovascular incidents, and renal insufficiency. In patients undergoing cholecystectomy for acute cholecystitis, diabetes increases the risk of mortality, cardiovascular events, and renal failure. Insulin-treated diabetics have more co-morbidities and poorer outcomes.