The sleep of people with dementia living in long-term care is known to be disturbed. This pre-post controlled pilot study examined the effects of a person-centered dementia care intervention on sleep in assisted living residents with dementia. The three-month intervention included in-class staff training plus supervision and support in practice. The sleep-wake patterns were measured using actigraphy for three consecutive days at baseline and postintervention. Sixteen residents from the intervention and six from the control groups completed the study. The intervention group had significantly more nighttime sleep at posttest. After adjusting for baseline, the intervention group exhibited significantly less daytime sleep and more nighttime sleep. Person-centered dementia care may be effective for improving sleep of residents with dementia.