Background: Sleep pattern is one of the most important issues which can affect mental development in adolescents. Objectives: This study was designed to asses sleep pattern and its relationship with depression in order to obtain information for planning interventional programs and health promotion in adolescents. Methods: This was a cross-sectional study conducted on high school students in Hamadan, Iran in 2019. Mean age of the students was 16.53 ± 0.69 years (Min - Max: 15 - 19), and 290 (50.3%) students were girls. Samples were selected by multiple cluster sampling method in which 576 students were enrolled in the study. Two standard, valid and reliable self-reported questionnaire was used for recording sleep pattern (PSQ) and depression (Beck). After data collection, SPSS was used for data analysis. All P values less than 0.05 were considered as significant. Results: Nearly 70% of the adolescents had problems in some subscales of sleep disorder included in mental quality of sleep, delay in falling asleep and daily dysfunction. Among them in 10% sleep duration was less than 5 hours and in 69% usual bedtime was after midnight (24 o’clock). Severe sleep problem in boys and students with fine educational status was more than others (P value < 0.001) and there was a statically significant correlation between sleep disorder and depression score (Pearson correlation: r = 0.42; P < 0.001) and in students with severe sleep disorder, 48.9% were severely depressed. Conclusions: Problems in mental quality of sleep was notable in Iranian adolescents, almost half of them had some degree of depression symptoms. Being boy and having severe problem in sleep pattern were predictors for depression. This information might be applied for well-being as well as physical and mental development interventional programs such as sleep health screening and adolescents and their parents’ educational programs in adolescents’ health promotion sector.