This article describes an innovative preventive occupational therapy intervention for well older adults, the Well Elderly Treatment Program. In a previously reported large-scale randomized effectiveness study, this intervention was found to be highly successful in enhancing the physical and mental health, occupational functioning, and life satisfaction of multicultural, community-dwelling elders. In this article, the philosophical background, manner of development, topical content, methods of program delivery, and mechanisms underlying the program's positive effects are discussed, along with implications for occupational therapy practice. The treatment was based on application of occupational science theory and research and emphasized the therapeutic process of lifestyle redesign in enabling the participants to actively and strategically select an individualized pattern of personally satisfying and health-promoting occupations. The wide-ranging effectiveness of the program supports the occupational therapy profession's emphasis on occupation in affecting health and positions practitioners to extend their services to the realm of preventive interventions.