<p><strong>Purpose: </strong>Previous work demonstrates a link between poor child sleep and increased caregiver mental health symptoms. In particular, children with NGS are known to experience severe and persistent sleep difficulties. Few studies have examined the association between child sleep disturbances and caregiver internalizing symptoms across families affected by neurogenic syndromes. More specifically, no study has examined how sleep disturbances in children diagnosed with NGS impact caregiver internalizing symptoms severity across development (from infancy to school-age children), using a longitudinal framework and multilevel analyses<em>. </em>Thus, the current study aims to test the effect of child sleep duration on caregiver mental health changes over the course of development (child age, from infancy to school-age children) in a mixed cohort of families affected by neurogenetic syndromes and a sub-group of neurotypical children. <strong>Method: </strong>A total of 193 caregivers were recruited, via web-based support groups, syndrome research registries, and social networks, as part of a broader longitudinal study, the Early Phenotype Study. To measure child sleep duration and caregiver internalizing symptoms, parents completed the Brief Infant Sleep Questionnaire and the Depression, Anxiety, and Stress Scale, respectively, at each time point yielding a total of 718 observations. Separate multilevel models were conducted for caregiver depression, anxiety, and stress in relation to child sleep duration at the between- and the within-person level with child age as a moderator. <strong>Results: </strong>Results of the present study revealed a between-person main effect of child sleep duration on caregiver symptoms of depression and a within-person effect of child sleep duration on stress symptoms in caregivers. The moderating effect of child age was not statistically significant across models. <strong>Conclusions: </strong>Overall, findings of the current study support previous literature and suggest child sleep duration may provide us with information on who may be at greater risk of exhibiting greater symptoms of depression, drawing the importance of focusing on improving child sleep duration as a way to reduce caregiver mental health challenges. </p>