The blending of polymers is an interesting route to obtain new materials with improved properties in an inexpensive way. The main polymer blends are immiscible and compatibilization is necessary to control the morphology and interfacial adhesion of these materials. Nanosized particles are being studied as compatibilizing, or at least morphology-stabilizing, agents for some blends, affecting the microstructure and improving some properties. Polystyrene-polypropylene polymer blends with different ratios were prepared in a twin screw extruder using organophilic clay as compatibilizer. Samples were collected through the screw of the extruder in order to evaluate the morphology development during the processing and understanding the clay migration and the role in the phase stabilization. The morphology of the blends were evaluated by SEM micrographs and showed the morphology development of the sample collected during and at the end of the extrusion. The morphology during the extrusion showed elongated and large particles while at the end of the process the dispersed phase is better dispersed. The morphology of the blends with ratios PP/PS of 30:70, 50:50 and 70:30 showed smaller domains with the use of organoclays and the elongated droplets could be seen at the 50:50 ratio. The mechanical properties changed as increasing the tougher material in the composition and the use of the clay improved the storage and tensile moduli of the materials.