Sleep is required for healthy and adaptive neurobehavioral and psychosocial functioning throughout the life course. Sleep is restorative, facilitates memory consolidation, improves immune function, and regulates emotional responses. Sleep deprivation, whether due to sleep disorders or other life conditions and transitions, is a significant risk factor for negative developmental outcomes at all stages in the life course. This article adheres to the biopsychosocial model to review current research describing the benefits of adequate sleep and ways in which insufficient sleep, as determined by developmental needs throughout the life course, can undercut healthy development. Particular attention is paid to social issues of relevance to social workers, with a closing discussion of policy and implications for future work within the field.