Although much research work has been conducted on the production and characterisation of polypropylene/organoclay nanocomposites, the effects of nanoscale fillers with respect to actual morphology through numerical modelling have been rarely addressed. This paper describes a unique development from fabrication and experimental characterisation to the numerical modelling of polypropylene/organoclay nanocomposites based on the real mapping of nano/microstructures. Twin screw extrusion is used with a two-step masterbatch compounding method to prepare such nanocomposites with organoclays (ranging between 1wt% and 10wt%) and maleated polypropylene (1:1 weight ratio). The material characterisation using X-ray diffraction (XRD), scanning electron microscopy (SEM) and dynamic mechanical analysis (DMTA) are conducted and mechanical properties are determined by tensile, flexural and impact tests. Finally, computational models are established by using an innovative object-oriented finite element analysis code (OOF) to predict the overall mechanical properties of nanocomposites.