Transition metal dichalcogenides (TMDs) have attracted considerable attention as active electrocatalysts for the hydrogen evolution reaction (HER). Since TMD catalysts are commonly supported on carbon to endow electrical conductivity, understanding the growth behaviour of TMDs on carbon surfaces is crucial, and yet remains to be explored. In this work, we investigated the growth behaviour of tungsten sulfide (WS_x) on carbon surfaces inside the confined nanopores. Experimental and computational studies revealed the preferential bonding between the basal planes of WS_x and carbon surfaces, as well as the subsequent horizontal growth of WS_x. As a result, subnanometer WS_x clusters were formed at a low WS_x loading, and grew into monolayer WS₂ nanoplates with increased WS_x loadings. In contrast, a TMD analogue, MoS₂, favors edge plane bonding with carbon surfaces and subsequent stacking of nanoplate layers, leading to multilayer MoS₂ nanoplates with increased MoS₂ loadings. A time-dependent growth of WS_x further corroborated the formation of WS₂ nanoplates at the expense of ultrasmall WS_x nanoclusters. Interestingly, the sample prepared with a short sulfidation time, which was mainly comprised of WS_x nanoclusters, showed higher HER activity compared to the sample prepared with a prolonged sulfidation time, which mostly contained WS₂ nanoplates. The higher HER activity of WS_x nanoclusters is attributed to the larger density of active bridging S₂²⁻ sites, compared to the WS₂ nanoplates. These findings may provide important insights into the growth behaviour of layered TMD materials at the nanoscale, as well as potential active species in WS_x for the HER.