Nanocomposites based on polyamide 6 have been directly prepared by melt compounding, using modified low cost bentonites by three selected quaternary ammonium cations, in particular quaternized octadecylamine (ODA), dimethyl benzyl hydrogenated tallow quaternary ammonium (B2MTH) and dimethyl hydrogenated ditallow quaternary ammonium (2M2TH). Thermal stability of organic modifiers and organoclays has been studied by TGA and results allow evaluating the degree of modifier incorporation into clay galleries. The influence of the organic modifier on the morphology and properties of the obtained nanocomposites has been studied by X-ray diffraction and TEM analysis. Depending on the degree of bentonite modification, different mechanisms were reported to explain the improved mechanical properties of the resulting nanocomposites.