Polypropylene/clay nanocomposites were studied with focus on optimization of mixing conditions. Two different types of commercial nanofillers Dellite(A (R)) were used (Dellite(A (R)) 72T and Dellite(A (R)) 67G). Effect of various concentrations of fillers on morphology and mechanical properties was investigated. Conditions of preparation were varied with respect to mixing time and speed of rotation of kneaders. Results of morphology study showed that nanocomposites contained agglomerates of nanofillers. The comparison of the filler types revealed that better dispersion and distribution was found for nanocomposites containing Dellite 72T which had also better tensile strength. Optimum mixing time was 30 min. 3D graphical analysis showed that the optimum speed of rotation was 60 rpm and with increasing clay content (2-10 wt%) the tensile strength increased.