The present work assesses the efficacy of an animal-assisted therapy (AAT) program in the reduction of neuropsychiatric symptoms in older adults with medium to severe dementia. Performed in an Alzheimer’s disease/dementia care unit, the intervention included 11 elderly residents aged 71 to 93 years (mean age = 82.91 years; mean Mini-Mental State Examination score = 7.8/30). Behaviors during the AAT sessions as well as pre/post intervention neuropsychiatric symptoms were examined during this 5-month weekly intervention conducted by an AAT-certified psychologist along with her dog. AAT had a positive effect on total score and caregiver distress score for several neuropsychiatric symptoms (i.e., delusion, depression, disinhibition, euphoria, and aberrant motor activity). Moreover, the ratings of the various behaviors during each session suggest that the beneficial effects of AAT appear during the first few sessions. These results support the notion that regular and long-term AAT sessions are an effective alternative to pharmacological interventions for the reduction of neuropsychiatric symptoms.