Abstract: Hydrogen, recognized as a clean energy source, highly depends on high-performance electrocatalysts for its efficient production. Although transition metal-based catalysts are low-cost and exhibit good activity, they suffer from issues such as agglomeration, poor conductivity, and insufficient stability. Carbon nanomaterials can effectively address these problems through a confined growth strategy, significantly enhancing the hydrogen evolution reaction (HER) performance and stability of the catalysts. Based on the dimensional differences of carbon materials, this article systematically reviews their application characteristics: one-dimensional materials (carbon nanotubes, nanowires, nanofibers), leverage axial confinement effects and high conductivity to effectively encapsulate nanoparticles, suppress agglomeration, and facilitate electron transfer; two-dimensional materials (graphene, carbon nanosheets) utilize in-plane anchoring and interlayer confinement to optimize catalyst dispersion and interfacial electronic structure; three-dimensional materials (carbon foam, porous carbon, carbon shells, etc.) enhance mass transfer and stability through hierarchical pore channels and three-dimensional confined spaces. The review focuses on the mechanisms through which carbon materials modulate catalyst morphology, size, electronic structure, and improve stability in both acidic and alkaline environments. Moreover, the current research limitations and future development directions are also pointed out.