Polypropylene (PP)/nylon 6/clay composites were prepared by compounding of PP, which had previously been treated with two kinds of silane compounds, with a master batch composed of 90 wt % of nylon 6 and 10 wt % of octadecyl amine-modified sodium montmorillonite (NM10). The morphology of the composites was investigated by means of SEM, TEM, XRD, and energy-dispersive X-ray analysis. All of the composites exhibited a phase-separated morphology, irrespective of whether the PP was modified with the silane compounds or not. However, adhesive strength between the modified PP and NM10 was stronger than that between neat PP and NM10. Moreover, the PP grafted with 3-(trimethoxysilyl)propyl methacrylate (PP2) reacted with the silanol groups of the clay to form PP-clay hybrid during the compounding, which acted as a compatibilizer for the PP/nylon 6/clay composite. PP2NM composite (PP2/NM10 80/20 on weight basis) exhibited a peculiar morphology, in that the PP-rich phase formed island domains within the nylon 6-rich domains, which were in turn dispersed in the PP-rich continuous matrix. (c) 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 607-615, 2007.