Block copolymers of nylon 6 with 10, 15 and 20% of poly (ether-esteramide) as elastomeric phase were synthesized by reactive processing. These materials are obtained by the anionic polymerization of epsilon-caprolactam in the presence of a linear prepolymer of poly (ether-esteramide) with a Grignard reagent. Differential Scanning Calorimetry (DSC), torque rheometry and formic acid test were used to characterize the obtained copolymers. The results showed that block copolymers of Nylon 6 were formed. The melting temperature and the crystallinity of the copolymer decreased when the elastomer phase content increased. Two Tg's appeared; the blocks of the copolymers were not miscible. We calculate the size of nylon 6 blocks for each composition. The physical-mechanical behavior was also studied. More flexible materials were obtained when the soft phase content in the copolymer was increased. The results of this work provide an important information for the synthesis of this kind of materials by reactive extrusion.