In this study, the effects of polyhedral oligomeric silsesquioxane (POSS) nanoparticles on the mechanical, morphological and thermal properties of polypropylene-polyamide 6 (PP/PA-6) blends were investigated. The POSS type and composition were the experimental parameters. Vertical force measurements indicating the on-line viscosity change of the melt during compounding showed that incorporation of POSS nanoparticles decreased the melt viscosity of PP/PA-6 blend. Scanning electron microscopy (SEM) revealed that the dispersed phase particles size was reduced in the presence of POSS. The mechanical test results showed that yield and impact strength increased as the POSS content of the nanocomposites increased from 1 to 5 wt% regardless of POSS type. Thermal behavior of the PA-6 component in the nanocomposites was determined by differential scanning calorimeter (DSC). An increment in the degree of crystallization of PA-6 was observed. It was obtained from the X-ray diffraction (XRD) analysis that incorporation PA-6 with gamma-crystals to the PP hindered the formation of beta-PP in PP crystallization. (C) 2016 Elsevier Ltd. All rights reserved.