Background: Bariatric surgery is the most effective treatment of morbid obesity and obesity-related conditions. Laparoscopic sleeve gastrectomy (LSG) has become increasingly popular in Denmark and worldwide. Objective: To evaluate long-term outcomes including postoperative complications after LSG. Setting: University Hospitals, Denmark. Methods: This was a nationwide multicenter cohort study including all patients who underwent LSG during 2010 to 2016 in Denmark. Data were collected from the Danish Obesity Surgery Registry and medical records. Representatives from all public bariatric centers in Denmark registered information on demography, indication, preoperative tests, operative information, weight loss, status of co-morbidities, and early and late complications. Results: In total, 541 patients were included in the study. Median follow-up was 6 years, and 536 patients (99%) were available at the end of follow-up. The patients achieved a persistent weight loss. Quality of life significantly improved after both 12 and 24 months. Overall, 3% of the patients had a major complication ≤30 days after the procedure and 3% underwent reoperation. One in 5 patients (22%) had an early minor complication. In the long term, 3% of the patients had a major complication and 24% of the patients had ≥1 minor complication. The most common surgery-related healthcare contacts addressed gastroesophageal reflux, weight recurrence, and stenosis symptoms. Conclusions: Patients after LSG achieved sufficient weight loss and improved quality of life. The procedure was safe with low risk of early and late major complications. However, there was a high frequency of early and late minor complications in 22% and 24% of the patients, respectively.