BACKGROUND: Physical inactivity in middle-aged and older adults is a major health problem. Exercise snacks are an emerging form of physical activity characterized by shorter single bouts of high-intensity exercise spread out repeatedly throughout the day which can provide more exercise opportunities for middle-aged and older adults. PURPOSE: To summarize perceptions and experiences of exercise snacks among middle-aged and older adults, and explore the barriers and facilitators of promoting exercise snacks. METHODS: We followed the PRISMA and systematically searched five databases from the earliest to May 2024. The Critical Appraisal Skills Program tool is used to quality assess and the Capability, Opportunity, and Motivation Model of Behavior (COM-B model) is used to guide thematic synthesis. RESULTS: Fourteen categories from nine studies were summarized, and 277 findings were identified. Three synthesized findings were: capability of middle-aged and older adults (including health-related exercise disorders, learning and mastery skills, and health literacy), opportunities for exercise snacks (including flexible and free, easy and quick, integration into life, social and family support, and application of mobile health technology), and motivation of exercise snacks (including pleasurable experiences, gaining physical and mental benefits, effective reminders, incentives and feedback, personalized needs, and self-efficacy). CONCLUSION: Exercise snacks are a promising approach， however, they need to be continuously optimized. Our results can provide evidence for designing and optimizing exercise snack programs. Medical workers should assist middle-aged and older adults in developing appropriate exercise snack strategies. TRIAL REGISTRATION: PROSPERO (CRD42024544089).