The multiwalled carbon nanotubes were directly compounded with poly(phenylene sulfide) (PPS) via melt mixing. The morphology and physical properties, including viscoelasticity, electrical conductivity, and thermal and mechanical properties, of the obtained composites were investigated. The results show that the purified nanotubes can be fully dispersed in the PPS matrix especially at low loading levels because of their good affinity. The composites hence present relative low rheological and electrical percolation thresholds. The presence of nanotubes, on the one hand, shows good reinforcement effect because of the strong interfacial interactions with the PPS matrix, which is confirmed by the strain overshoot flow behavior, and, on the other hand, acts as a nucleation agent, promoting crystallization of the PPS matrix. Both contribute to evident improvement of tensile strength and dynamic mechanical properties of the composites. POLYM. ENG. SCI., 49:1727-1735, 2009. (C) 2009 Society of Plastics Engineers