Objective:The aim of the present study was to determine the relationship between night eating symptoms(NES) and body mass index(BMI) in preclinical medical students and to examine the potential mediating role of impulsivity, depressive symptoms and sleep-related factors in this relationship. Method:The study included 408 preclinical medical students. All participants were asked to complete the sociodemographic information form, Night Eating Questionnaire(NEQ), Pittsburgh Sleep Quality Index(PSQI), Barratt Impulsiveness Scale-11(BIS-11), and Patient Health Questionnaire Depressive Symptom Scale(PHQ-9). Results:The mean age of the participants was 19.94±1.50 years; 235(57.6%) of the participants were female. A significant positive correlation was identified between the NEQ score and BMI of the participants(r=0.146;p=0.004). A moderate but significant correlation was observed between the NEQ score and BIS-11(r=0.328), PHQ-9(r=0.446) and PSQI scores(r=0.503) of the participants. Sleep quality was found to mediate the relationship between NES and BMI(β=-0.066, S.E.=0.020, 95% CI[-0.080, -2.814]) while impulsivity and depressive symptoms did not(p>0.05). Examination of the relationship between sleep quality sub-dimensions and NEQ indicated that PGQI-2(sleep latency) played a mediating role(β=-0.051, S.E.=0.014, 95% CI[-0.057,-0.005]), while the other sub-dimensions did not. Discussion:The findings of our study support the existence of a relationship between NES and BMI. Among the potential mediators in this relationship, a mediating role of sleep quality rather than depressive symptoms and impulsivity, was identified. Sleep latency, a component related to sleep quality, was found to have an effect on BMI. Future studies are needed to investigate the effectiveness of interventions aimed at improving sleep hygiene in order to control weight gain in NES patients.