The electrical transport behavior of carbon nanotube field-effect transistors (CNT-FETs) decorated with gold nanoparticles (NPs) has been investigated. After decoration with Au NPs, the Ion/Ioff ratios of nanotube FETs decrease and some of the p-type devices even change into metallic ones. The Au NPs decrease the contact resistances between the CNTs and metal electrodes, and accordingly increase the on-state electric currents of the CNT-FETs. The possible mechanisms for the effects of NPs on electrical transport properties of the CNTs have been analyzed qualitatively. Our investigations are closely linked with some promising applications of carbon nanotube hybrid materials in nanoelectronics.