Background Carotid endarterectomy is the gold standard operation to prevent stroke in patients with symptomatic carotid artery stenosis and asymptomatic high-grade carotid artery stenosis. Longer operative times for different operations have been shown to affect the outcomes adversely. The purpose of this study was to determine the incidence of postoperative complications after carotid endarterectomy, and their relation to the operative times. Methods The American College of Surgeons database was queried for all patients who underwent carotid endarterectomies from 2005 to 2007. Patients were divided into 2 groups based on the operative time (<140 min and >140 min). The incidence of preoperative morbidities and postoperative complications was then compared among these groups. Results A total of 10,423 patients underwent carotid endarterectomies during this time period. Longer operative time (>140 min) is associated with higher incidence of 30-day mortality (1.3% vs. 0.7%, P = 0.013), length of stay ≥7 days (12.7% vs. 8.1%, P < 0.001), postoperative pneumonias (1.6% vs. 0.9%, P = 0.001), failure to wean from ventilator for more than 48 hr (1.8% vs. 0.6%, P < 0.001), and return to the operating room (6.5% vs. 5.2%, P = 0.010). Factors associated with longer operative times were the following: age <65 years (odds ratio [OR] 1.3, confidence interval [CI] 1.1–1.6), male gender (OR 1.6, CI 1.4–1.7), black race (OR 1.5, CI 1.2–1.8), history of myocardial infarction (OR 1.7, CI 1.2–2.4), higher American Society of Anesthesiologist score (OR 1.3, CI 1.1–1.6), presence of surgical trainees (OR 3.6, CI 1.7–7.4), and presence of surgical fellows (OR 1.7, CI 1.4–2.2). Conclusions Longer operative times for carotid endarterectomy are associated with increased risk of postoperative complications. Factors associated with longer operative times for carotid endarterectomy can be identified preoperatively.