Investigating sleep patterns and prevalence of sleep problems among children, particularly at the first year of school, is the main objective of the current study. After evaluating sleep pattern and common bedtime problems among children, a number of factors related to these issues were also addressed. Methods: The statistical population of the cross-sectional study includes all the first-grade students of elementary schools around Kermanshah City in western Iran, among which a sample of 644 participants were selected. The sampling method was a multi-step clustering method and the obtained data were analyzed using Pearson's correlation and binary logistic regression analyze. Results: The results of the study show that 30.7% of the participating children suffer from resistance to falling asleep, 15.8% suffer from resistance to waking up from sleep, 13.9% suffer from waking up during sleep, 26.1% suffer from insufficient sleep, and finally 11.2% suffer from sleep-disordered breathing. Accordingly, sleep quality among 7.6% of the children was poor; this factor was 5.1% among girls and 10.3% among boys (P < 0.01). Moreover, there was a significant relationship between sleep hygiene and sleep problems (P < 0.001). Especially, components of planning/worrying (OR = 0.49-1.84) and exercise (OR = 0.73-1.34) are main predictors of sleep problems. Conclusions: Based on the results of the study, it can be said that 57% of the first-grade students suffer from at least one sleep problem. Poor sleep hygiene is an important predictor for sleep problem in the first-grade students.