BACKGROUND: The demand for wearable technologies has surged in recent years, demonstrating remarkable potential, especially in health promotion. However, there is currently a lack of clarity about the types and roles of wearable devices in health care of older adults. OBJECTIVE: This review aims to provide a comprehensive overview and categorize the current research conducted with wearable devices for health promotion and disease prevention in older adults. METHODS: We conducted a systematic literature review using the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) framework and synthesized the results. A total of 6 databases were searched to identify wearable devices reported in studies from inception to July 28, 2024. Titles, abstracts, and full texts were independently screened by 2 reviewers. Any discrepancies were resolved by a third reviewer when necessary. The types of results from relevant studies were systematically mapped into predefined categories. RESULTS: Based on the inclusion criteria, 109 studies were included. The most commonly reported health targets of wearable devices were mobility, mental health, fall-related, arrhythmia detection, activity recognition, disease diagnosis, and sleep monitoring. Most studies were application design and observational study, and in European countries and the United States, 51 studies of the participants were healthy. The most popular anatomical landmarks for wearable placement were the wrist, waist, and chest. Two evaluation approaches for wearable devices were used: performance metrics in controlled settings and real-world assessments with end users. The opportunities presented by wearable devices are countered by multiple challenges, including data availability and reliability, technical limitations, utility and user acceptance, cost, security and privacy, performance gaps, and challenges. CONCLUSIONS: Wearable devices hold great promise for promoting health in older adults, but several hurdles remain for full adoption. A broader and more diverse group of older adults is needed to identify the most beneficial wearables and to optimize the technology. Further studies are required to statistically synthesize real-world performance and evaluation results. We hope that this review will serve as a valuable reference for the development of wearable devices in older adults.