Diabetes mellitus is a chronic disease requiring multifunctional natural agents. Arctium lappa is traditionally used in Eastern and European medicine to address metabolic disorders. This comprehensive narrative review, conducted between 2000 and 2025 using international databases (Scopus, PubMed, Web of Science Core Collection, and Google Scholar), evaluates the species through its ethnomedicine, phytochemistry, preclinical evidence, and safety. The available evidence suggests that A. lappa exerts antidiabetic effects via multi-layered mechanisms, including AMPK activation, insulin signaling modulation, and increased GLUT4 translocation. Key bioactives (arctigenin, arctiin, and inulin) collectively improve insulin sensitivity and lipid metabolism. However, preclinical studies confirm these effects in animal models, while limited clinical data in non-diabetic cohorts focus on systemic inflammation. This highlights a significant gap in randomized controlled trials targeting glycemic control in diabetic populations. In this context, while A. lappa shows promise as a potential metabolic regulator; this evidence is currently derived primarily from in vitro and animal models. Systematic clinical trials are urgently required to establish glycemic efficacy in humans, validate its therapeutic potential, and determine the optimal dosage and safety profile. This review evaluates the multi-targeted biological potential of A. lappa to guide future research and evidence-based application.