In recent years, nanomaterials have led to promising developments in the improvement of pavement performance. In this study, characterisation of nanocomposite-modified binders using Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), and dynamic shear rheometer was investigated. The study investigates the application of response surface methodology (RSM) to develop models and determine optimum proportions for higher linear viscoelastic properties. FT-IR spectroscopy confirms chemical reaction between nanosilica- and polypropylene-modified bitumens, which resulted in a reduction in oxidative hardening of the modified binders. FE-SEM analysis for the modified binders shows a good dispersion of polypropylene and nanosilica within the modified binder matrix. RSM statistical analysis shows a high correlation coefficient (R2) of 0.9959, 0.9972, and 0.9964 for the responses complex modulus, phase angle, and viscosity. This indicates that the experimental values analysed are in real agreement with the developed models. Analysis of the individual effects of the independent variables temperature and nanosilica content reveals that all the responses are influenced by the interaction of both the two independent variables, but temperature shows a strong influence in the complex modulus and complex viscosity responses than nanosilica content. Numerical optimisation results using the models developed show that an optimum mix can be achieved with 1 nanosilica at a temperature of 30�C. © 2018, King Fahd University of Petroleum & Minerals.