Background: The repeated episode of obstructive hypopnea and apnea during sleep is defined as obstructive sleep apnea (OSA) and it is a common condition in obese patients. Studies performing bariatric surgery have demonstrated a significant improvement in OSA by weight reduction. In this prospective study we aimed to explore the efficacy and safety of Laparoscopic Sleeve Gastrectomy (LSG) on OSAS among severely obese patients. Material and Methods: A total of 32 morbidly obese patients who underwent LSG for morbid obesity were included in this study. Body weight, height, body mass index (BMI) and standard overnight polysomnography (PSG) were measured at before and after LSG at the 6th month. Results: 32 patients (27 female, 5 male) who have postoperative PSG's were included in this study. The mean age was 43.22±9.87 years old. The mean preoperative and postoperative BMIs were 50.36±8.14kg/m² and 37.27±7.93kg/m², respectively. The mean Epworth sleepiness scale determined as 5.84±4.65 preoperatively and 2.19±3.55 postoperatively. The preoperative and postoperative sleep efficiency test of the patients was determined as 83.34±9.68 and 88.94±6.90 respectively. AHI average at the preoperative PSG was 31.47±26.34, while 9.35±10:34 at postoperative 6 months and found as statistically significant. Conclusion: Our data showed that LSG is an efficient and safe procedure on severely obese patients and showed a predictive remission of clinical and sleep parameters of patients with OSA by analyzing PSG data during the first 6 months.