The aim of the present study was to explore potential factors of inadequate sleep health (i.e. sleep duration, quality, and timing) of school-aged children. Data were collected among 382 primary school children (aged 4–13 years) and their parents. Personal characteristics (i.e. age, sex), individual lifestyle behaviours (i.e. screen use, sleep hygiene behaviour), social and community factors (i.e. parental sleep-related practices, parental barriers, perceived ethnicity), and living conditions (i.e. parental educational level, sleep environment) were assessed with a parental questionnaire. Sleep duration, quality, and timing were assessed with a sleep diary. Associations were analysed using linear mixed models and logistic regression analyses. In total, 332 children, with a mean (range) age of 7.5 (4–13) years, were included in the analyses. The mean sleep duration was 632 min/night, the mean sleep quality score was 40, on a scale from 10 to 50, and 25% had a bedtime that varied >40 min between weekdays. Factors negatively associated with children’s sleep health included older age, perceived non-Dutch cultural background, lower parental pre-sleep emotional support, the parental barrier to get their child to bed on time when siblings have a later bedtime, high parental educational level, sleeping in a darkened bedroom, and being brought to bed after falling asleep. On average, children in the present study had adequate sleep health. The factors found to be associated with children’s sleep health are useful for future healthy sleep research and intervention development.