The objective of this study was to compare the effect of multisensory stimulation environment (MSSE) and one-to-one activity sessions in the symptomatology of elderly individuals with severe dementia. Thirty-two participants were randomly assigned to the following 3 groups: MSSE, activity, and control group. The MSSE and activity groups participated in two 30-minute weekly sessions over 16 weeks. Pre-, mid-, and posttrial; 8-week follow-up behavior; mood; cognitive status; and dementia severity were registered. Patients in the MSSE group demonstrated a significant improvement in the Neuropsychiatric Inventory and Bedford Alzheimer Nursing Severity Scale scores compared with the activity group. Both MSSE and activity groups showed an improvement during the intervention in the Cohen-Mansfield Agitation Inventory aggressive behavior factor and total score, with no significant differences between groups. The MSSE may have better effects on neuropsychiatric symptoms and dementia severity in comparison with one-to-one activity sessions in patients with severe dementia.