Objective: The relationship between night eating syndrome (NES) and obesity resembles a vicious circle. The pre-sence of NES facilitates the shift to obesity, whereas the NES is more common in obese individuals. In the literature, the frequency of NES is reported as 2-20% in individuals with morbid obesity. In addition to obesity, the presence of NES was associated with higher depression scores and lower self-esteem. The aim of this study was to investi-gate the prevalence of NES and related factors in morbid obesity patients. Methods: In this study, 452 patients who applied for psychiatric evaluation before the bariatric surgery were evaluated. The presence of psychiatric disorder was assessed by a clinical interview conducted by a psychiatrist. Sociodemographic and clinical features such as age, gender, education level, body mass index were also recorded. Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI), Rosenberg Self Esteem Scale (RSES), and Night Eating Questionnaire (NEQ) were administered. Results: Fifty-nine (13%) of 452 morbid obesity patients were found to have NES. BDI, BAI, and RSES scores were significantly higher in the group with NES than without NES. In the group with NES, compared with non-NES; the rate of psychiatric disorder (44.1% and 26.2%, respectively) and depressive disorder (respect-tively, 25.4% and 13%) were significantly higher. The risk of developing NES in smokers increased by 3.05 fold; and a 1 unit increase in the BDI increases the risk of developing NES by 1.05 fold in the morbid obez sample. Discussion: In our study, it was found that comorbidity of NES in morbid obesity patients increased the risk of psychi-atric disease, especially depression, and self-esteem was worse in these patients. The fact that smoking is the highest predictor factor for the presence of NES is a finding that has been shown in other studies. The long-term follow-up studies are needed to investigate changes in depression, NES and eating patterns after bariatric surgery. [Anadolu Psikiyatri Derg 2019; 20(6.000): 605-612]