Extracellular vesicles derived from human umbilical cord mesenchymal stem cells (hucMSCs-EVs) represent a promising cell-free therapeutic strategy in regenerative medicine and oncology. These vesicles exhibit low immunogenicity, are non-invasively sourced, and possess multiple regenerative properties. This review examines the biogenesis of EVs and distinctive features of hucMSCs-EVs compared to other MSC-derived EVs. We explore their molecular mechanisms and preclinical efficacy across multiple organ systems, including nervous, locomotor, respiratory, circulatory, digestive, urinary, reproductive, and hormonal. HucMSCs-EVs demonstrate a dual role: promoting tissue repair through immunomodulation, angiogenesis, and anti-apoptosis in regenerative contexts, while exerting microenvironment-dependent pro- or anti-tumor effects in oncology. Despite promising preclinical results, clinical translation requires overcoming challenges such as standardized production, delivery optimization, and safety evaluation. As multifunctional biological nanotherapeutics, hucMSCs-EVs show transformative potential for treating multisystem diseases. However, their universal applicability is constrained by heterogeneity, biodistribution limitations, and environment-dependent efficacy. Future work should focus on scalable manufacturing, targeted delivery strategies, and rigorous clinical trials to realize their full therapeutic potential.