Horticultural therapy (HT) is used across the lifespan with individuals with a wide range of physical, social, and cognitive abilities. Older adults make up a large group of participants in horticultural activities. As the population of older adults grows, more adults face the risk of experiencing a dementing illness. Many families turn to institutional care programs, such as nursing homes and adult day service (ADS) programs, for assistance with the care of their relative with dementia. HT may be an appropriate activity to incorporate into dementia care activity programs, but formal evaluations of such programs are limited. The current study evaluated a 10-week HT program conducted with adults with dementia at an ADS program. Observations indicated that participants engaged in the horticultural activities for greater periods of time than the nonhorticultural activities. Participant affect during the horticultural and nonhorticultural activities was comparable. HT is appropriate for dementia care programs serving adults with a wide range of cognitive, physical, and social needs, and it should be considered as a viable alternative to more typical dementia care program activities.