Objectives: An increasing number of children and adolescents divide their time between their separated parents' homes. Although marital conflict is disadvantageous for children's sleep, little is known about how children of separated parents sleep. The objective was to investigate the association between children's cus-tody arrangements and sleep habits and sleep initiation difficulties. Design: Cross sectional nationally representative samples of adolescents from the WHO study Health Behav-iour in School-aged Children (HBSC) (n = 11,802). Setting: Sweden in 2013/2014 and 2017/2018. Participants: Adolescents in grades 5, 7, and 9 from Swedish compulsory comprehensive school. Measurements: The survey included questions on sleep behaviors including bedtime, wake-up time and fre-quency of sleep onset problems. The analysis methods used were ordinary least squares and logistic regression. Results: The results show differences by custody arrangement, but they are not uniform across the dependent variables. Children and adolescents in sole maternal custody were less likely to sleep as much as recommended (P < .001), more likely to have late bedtimes (P < .001), report sleep initiation difficulties (P < .01) and to report social jetlag between school mornings and weekends (P < .05) compared to those in 2-parent families. Shared physical custody was associated with a higher likelihood of late bedtimes (P < .05) and sleep initiation difficulties (P < .05) compared to those in 2-parent families, but not of sleeping less than recommended or reporting social jetlag. Less-than-equal sharing was generally associated with worse sleep than in 2-parent families. Conclusions: As custody arrangements seem to be associated with sleep, it is important to understand the mechanisms behind the findings.