Background: Population ageing is accelerating worldwide, increasing the prevalence of chronic diseases and exposing older adults to heightened biological, social, and environmental vulnerabilities. Understanding vulnerability and the tools used to assess it is essential for developing person-centered health policies and care models. This systematic review aimed to identify vulnerability factors in adults aged 65 years and older. Methods: The review will be outlined according to the PRISMA guidelines and was registered in PROSPERO (CRD420251039796). Searches were conducted in PubMed, CINAHL, Scopus, Web of Science, and Google Scholar using controlled vocabulary and keywords related to vulnerability, frailty, functional impairment, geriatric assessment, health indicators, and quality of life. Eligible studies included older adults (≥65 years) and examined vulnerability through validated tools or structured assessment models. Exclusion criteria comprised studies involving non-validated scales, populations under 65, and research focused on COVID-19, climate change, or natural disasters. Methodological quality was assessed independently by two reviewers using Joanna Briggs Institute tools. The data will be extracted and organized into a structured table, including study characteristics, vulnerability predictors, assessment instruments, and health-related outcomes. Discussion: The review is expected to facilitate the timely identification of vulnerability patterns and support the integration and adaptation of healthcare models. Its findings will provide a basis for developing practical recommendations for professionals, managers, and policymakers, while refining assessment practices and guiding early detection strategies and evidence-based interventions to improve the health, autonomy, and quality of life of older adults.