Polyamide-6-montmorillonite composites have been prepared through melt blending and by anionic in situ polymerization using extruder equipment. The effect of the processing conditions on the structure and physical, mechanical, thermal, and rheological properties of the nanocomposites are studied. The nanocomposites have a high tensile modulus, higher softening point, and lower moisture regain and coefficient of linear thermal expansion in comparison with virgin polyamide-6. It is found that the physicochemical properties of composites prepared by both methods can be at the same level during the optimal choice of the organic modifier of montmorillonite and process conditions. © 2013 Pleiades Publishing, Ltd.