Multiwalled carbon nanotubes (MWCNTs)/Cd0.8Zn0.2S nanocomposites were synthesized via the simple co-precipitation of pretreated MWCNTs, acetates and sodium sulfide. The photocatalytic activities for hydrogen production of the produced MWCNT5/Cd0.8Zn0.2S with different amount of MWCNTs were systematically investigated under visible-light (lambda >= 420 nm) irradiation. Enhanced photoactivity of the nanocomposite was observed and can be attributed to the synergetic effect of its components' intrinsic properties, such as excellent light absorption and charge separation on the interfaces between the modified MWCNTs and Cd0.8Zn0.2S. It is also found that the nanocomposite with 15 wt% MWCNTs shows a higher photocatalytic hydrogen production efficiency and photostability than the pristine CdS and Cd0.8Zn0.2S nanoparticles. The MWCNTs/Cd0.8Zn0.2S nanocomposite holds promise for hydrogen production by improving the visible-light-driven photoactivity and photostability of Cd0.8Zn0.2S. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.