BACKGROUND A healthy lifestyle may protect against cognitive decline. We examined outcomes in elderly individuals after 18 months of a five-group intervention program consisting of various modalities to prevent cognitive decline. METHODS We conducted a cluster randomized controlled trial assessing 460 community-dwelling individuals aged 60 years and older in a geriatric community mental health center in Suwon, Republic of Korea, between 2008 and 2010. We developed an intervention program based on the principles of contingency management, which could be delivered by ordinary primary health workers. Group A (n = 81) received standard care services. Group B (n = 80) received bimonthly (once every 2 months) telephonic care management. Group C (n = 111) received monthly telephonic care management and educational materials similar to those in group B. Group D (n = 93) received bimonthly health worker-initiated visits and counseling. Group E (n = 94) received bimonthly health worker-initiated visits, counseling, and rewards for adherence to the program. RESULTS The primary outcome was the change in Mini-Mental State Examination (MMSE) scores from baseline to the final follow-up visit at 18 months. Group E showed superior cognitive function to group A (adjusted coefficient β = 0.99, p = 0.044), with participation in cognitive activities being the most important determining factor among several health behaviors (adjusted coefficient β = 1.04, p < 0.01). CONCLUSIONS Engaging in cognitive activities, in combination with positive health behaviors, may be most beneficial in preserving cognitive abilities in community-dwelling older adults.