This study will contribute to the identification and understanding of the reinforcement mechanisms of thermoplastic matrices by nanofillers. This aspect is addressed through the investigation of the thermal and mechanical properties of nanocomposites consisting of a polyamide 12 (PA12) matrix crammed with organically modified clay nanoparticles. An efficient approach to the synthesis of polyamide 12 (PA12) nanocomposites was investigated; Maghnite may be a processed Algerian mineral clay which will act both as a catalyst and as an inorganic reinforcement. Two sorts of organic substances were used, labeled CTA-Mag (1CEC) and CTA-Mag (2CEC), modified by cetyltrimethylammonium (CTA) ions. However, PA12/CTA-Mag nanocomposites are characterized by various physico-chemical techniques, XRD, FTIR, TGA, scanning and transmission electron microscopy (SEM and TEM). Measurements of tensile modulus, yield strength, lastingness, elongation at break and toughness were done to assess the behavior of the mechanical properties. Furthermore, we have analyzed the consequences of the mass fraction of the fillers on the structural, thermal and mechanical properties of those nanocomposites. Specific attention has been paid to the study of relationships between the macroscopic properties and therefore the structure of nanocomposites. Thermomechanical tests showed a big improvement within the properties of the nanocomposites compared to neat PA12.