Blends of polyphenylene ether (PPE), high impact polystyrene (HIPS) and styrene-butadiene-styrene (SBS) triblock copolymer with different concentrations of nano-fillers (nano-SiO2 or nano-TiO2) have been compounding by melt mixing using an internal mixer. The rheological, dynamic mechanical and mechanical properties of PPE/HIPS/SBS blends were investigated by means of oscillatory rheometry, dynamic mechanical analysis (DMA) and Izod impact measurements to determine the effect of the nano-fillers on the blends properties. The test results showed that the blends properties are affected when the processing conditions (order of addition of the components to the internal mixer and addition time of nano-fillers) are modified.