Sleep problems are common in Rett syndrome and other neurogenetic syndromes. Actigraphy is a cost-effective, objective method for measuring sleep. Current guidelines require caregiver-reported bed and wake times to facilitate actigraphy data scoring. The current study examined missingness and consistency of caregiver-reported bed and wake times from paper sleep diaries and actigraphy event mark button presses in a sample of 38 individuals with Rett and related syndromes (aged 2-36 years, mean = 13.1) across two 14-day collection time points. Rates of missingness and discrepancy between the 2 sources were relatively high and correlated with clinical severity and quality of life. Overall, the results suggest a need for alternative actigraphy scoring methods that do not rely on caregiver report in this population.