Sleep is vital for optimal physical and mental health, as well as cognitive and social functioning. Young adults with developmental disabilities (DD) are at greater risk for physical and mental health disorders and experience limitations in cognitive and social functioning in ways that can prevent participation in meaningful activities associated with young adulthood. Sleep literature has reflected that persons with DD experience worse sleep than persons without DD. Suboptimal sleep could compromise functionality and thus participation in young adulthood activities. Not much is known however of the nature of sleep problems experienced by young adults with DD. This study is a short-term longitudinal descriptive study on the sleep of young adults with DD using actigraphy. Results identify potential sleep problems with getting enough sleep and maintaining sleep. With a better understanding of sleep issues, efforts can be made to improve the sleep, functionality, and outcomes for young adults with DD.