Poor or short sleep and the presence of snoring indicative of sleep-disordered breathing (SDB) have been associated with behavioral problems in school-aged children. We examined the relationship between SDB, sleep duration, obesity risk, and behavioral characteristics in Japanese elementary school students using a large-scale survey. We conducted a cross-sectional study of children enrolled in all 46 public primary schools in Matsuyama city, Japan. The children's parents or guardians completed a questionnaire that covered sleep habits, presence of SDB risk, and behavioral characteristics. In total, 24 296 responses were received (90% response rate). After excluding incomplete responses, we analyzed complete datasets for 17 769 children. Mean sleep duration decreased with age, as did the prevalence of pediatric SDB. We found an increased risk for the presence of SDB and short sleep among overweight/obese children. With SDB or short sleep, we observed significantly increased odds of restless behaviors, fidgety behaviors, and poor concentration in school. Shorter sleep duration was associated with increased risk of obesity, and in turn, obesity increased SDB risk. Both short sleep duration and SDB risk were significantly associated with behavioral problems in school.