The high prevalence of sleep-related disorders is well documented in individuals with Down syndrome (DS). Given the association between physical activity (PA) and sleep in the typical populations, this study was the pilot study to examine this association through the parental report in this population. The total of forty-three individuals with DS (aged 14-55) participated in the present study. Parents reported on the questionnaires to measure different levels of PA and four factors of sleep-related disorders in adolescents and adults with DS. Our results indicate that age was positively associated with the frequency of "disorders of initiating and maintaining sleep". In addition, the levels of moderate-to-vigorous PA (MVPA) were negatively associated with the severity of "Features associated with obstructive sleep apnea (OSA)". Further, the active group had lower parental reports of features associated with OSA compared with the insufficiently active group after controlling for anthropometric measures. Our study suggests moderate-to-vigorous exercise may reduce OSA severity in individuals with DS. Therefore, future support for recreational services should be provided to promote physical leisure activity that may reduce the onset of sleep disorders in this population.