Laparoscopic sleeve gastrectomy (LSG) is effective as a stand-alone bariatric procedure. Despite its positive effect with regard to weight loss and improvement of obesity-related co-morbidities, some patients develop gastroesophageal reflux symptoms postoperatively. The pathogenesis of these symptoms is not completely understood. Hence, this study aimed to assess the effect of sleeve gastrectomy on acid and non-acid gastroesophageal reflux, reflux symptoms and esophageal function. In a prospective study, patients underwent esophageal function tests (high-resolution manometry (HRM) and 24-h pH/impedance metry) before and 3 months after LSG. Preoperative and postoperative symptoms were assessed using the Reflux Disease Questionnaire (RDQ). In total, 20 patients (4 male/16 female, mean age 43 ± 12 years, mean weight 137.3 ± 25 kg, and mean BMI 47.6 ± 6.1 kg/m(2)) participated in this study. GERD symptoms did not significantly change after sleeve gastrectomy, but other upper gastrointestinal symptoms, particularly belching, epigastric pain and vomiting increased. Esophageal acid exposure significantly increased after sleeve gastrectomy: upright from 5.1 ± 4.4 to 12.6 ± 9.8% (p = 0.003), supine from 1.4 ± 2.4 to 11 ± 15% (p = 0.003) and total acid exposure from 4.1 ± 3.5 to 12 ± 10.4% (p = 0.004). The percentage of normal peristaltic contractions remained unchanged, but the distal contractile integral decreased after LSG from 2,006.0 ± 1,806.3 to 1,537.4 ± 1,671.8 mmHg · cm · s (p = 0.01). The lower esophageal sphincter (LES) pressure decreased from 18.3 ± 9.2 to 11.0 ± 7.0 mmHg (p = 0.02). After LSG, patients have significantly higher esophageal acid exposure, which may well be due to a decrease in LES resting pressure following the procedure.