Objectives <p>Youth sleep is commonly measured through caregiver reports, youth self-reports, and more objective tools such as Fitbits. However, discrepancies between methods raise concerns about accuracy and the best approach for assessing youth sleep patterns. Few studies compare all three approaches, and little is known about how caregiver factors contribute to these discrepancies. This study examined agreement across caregiver-, youth-, and Fitbit-measured sleep and evaluates how demographic and family factors influence these discrepancies. </p> Methods <p>Data were drawn from participants who completed sleep-related measures at the 2-year follow-up in the ABCD Study (<i>N</i> = 4,328). Sleep duration was measured via Fitbit and youth and caregiver reports. Sleep quality was assessed using youth and caregiver reports.</p> Results <p>Correlations between sleep measures were significant but modest (<i>rs</i> = 0.13 to 0.30). Intraclass correlation coefficients indicated poor reliability across measurement techniques (ICC = 0.06 to 0.18). Both caregivers and youth overestimated sleep compared to Fitbit by 1.25 and 1.67&#xa0;h, respectively. Fitbit-caregiver discrepancies were lower for caregivers with less education, female youth, and Latine non-White youth, but youth-caregiver discrepancies were higher in families with less-educated caregivers, lower income, lower caregiver monitoring, and NHL Black youth.</p> Conclusion <p>Analyses demonstrate poor alignment between caregiver-, youth-, and Fitbit-based sleep measures, suggesting these tools capture different aspects of the sleep experience. Sociodemographic factors differentially predicted measurement disagreement based on method comparison, with greater caregiver monitoring associated with better youth-caregiver alignment. Findings support integrating wearable, caregiver, and youth reports within a family-centered framework for pediatric sleep research and care.</p>