In this study, the effect of triphenyl phosphate (TPP), commonly used as flame retardant, also montmorillonite nanoclay and hybrid of them, on the morphology and rheological characteristic of PC/ABS (Polycarbonate/Acrylonitrile butadiene Styrene) blends are investigated. The blends were prepared via a direct melt blending process in a twin-screw extruder. Morphological properties were characterized by scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The results for the variations of complex viscosity (eta*) with angular frequency (omega) showed a good agreement with those obtained from Carreau model. A plateau modulus (G(N)degrees) was observed in the blends containing nanoclay, indicating the formation of a network structure that increases the modulus as the results of the intercalation of silicate layers of nanoclay. The complex viscosity is increased with the inclusion of nanoclay and TPP, but the effect is more evident with nanoday. Also, the addition of nanoclay significantly enhances the non Newtonian behavior of PC/ABS blends, particularly at low-frequencies. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 1796-1804,2010