Abstract Frailty and multimorbidity are prevalent, interrelated geriatric conditions whose co-occurrence substantially elevates the risk of disability, hospitalisation, and mortality in older adults. Comprehensive Geriatric Assessment (CGA) is a multidisciplinary diagnostic process proposed as the gold standard for managing these complex conditions. A systematic literature review was conducted following PRISMA 2020 guidelines, searching PubMed, MEDLINE, EMBASE, CINAHL, Web of Science, and Google Scholar for peer-reviewed articles published between 2018 and 2025. Fourteen articles meeting predefined inclusion and exclusion criteria were selected and appraised using the Critical Appraisal Skills Programme (CASP) framework and an evidence-grading matrix. Included studies confirmed a bidirectional relationship between frailty and multimorbidity, mediated by chronic low-grade inflammation, immunosenescence, hormonal dysregulation, and sarcopenia. CGA was consistently effective in quantifying frailty severity, guiding individualised care planning, reducing hospital length of stay, and delaying frailty progression. Updated evidence from 2024 and 2025 confirms that CGA significantly reduces mortality risk and preserves independence in activities of daily living across hospital and community settings. The geriatric triangle, the interplay between frailty, multimorbidity, and polypharmacy, represents an important emerging framework for integrated geriatric management. Standardised CGA implementation, supported by validated digital frailty indices and multidisciplinary teams, is recommended to optimise outcomes.