This randomized controlled study tested the effectiveness of individualized activities, led by certified nursing assistants (CNAs), to increase positive affect and reduce negative affect and behavior among nursing home residents (NH) living with dementia. Residents with mild to advanced dementia (n = 180) were randomly assigned to usual care (n = 93) or 1 of 2 experimental conditions. Results show that residents were happier and less angry during an individualized positive psychosocial intervention compared with a standardized intervention. Even brief CNA-led individualized activities were effective in enhancing positive affect and engagement in persons with dementia.