Multiwalled carbon nanotubes (MWCNTs)/CdS nanocomposites containing different MWCNT contents were synthesized hydrothermally via direct growth of CdS nanoparticles on the functionalized MWCNT surface. The effects of the hydrothermal temperature and MWCNT content in the nanocomposites on the photoactivity for hydrogen production were investigated comparatively under visible light (lambda >= 420 nm) irradiation. It was found that 10 wt % MWCNTs/CdS showed much higher photocatalytic hydrogen production efficiency and photostability than the pure CdS nanoparticles. The significantly enhanced photoactivity of the nanocomposite was attributed to the synergetic effect of the intrinsic properties of its components, such as excellent charge transfer and separation on the interfaces between the modified MWCNTs and CdS nanoparticles, resulting from the direct growth of CdS nanoparticles on the MWCNT surface during the hydrothermal process. The present MWCNTs/CdS nanocomposite reveals obvious predominance, such as enhanced visible-light-driven photoactivity and photostability of CdS for hydrogen production.