Starlike block copolymers of Nylon-6 and polyurethane were synthesized using E-caprolactam as a monomer, caprolactam magnesium bromide as a catalyst, and a star prepolymer of polyurethane. These copolymers were compared with the linear block copolymers of Nylon-6 and polyurethane. Such copolymers were obtained using the reaction injection-molding process (RIM) of E-caprolactam at different contents of polyurethane (5-30 wt %). In increasing the content of the soft phase, in FTIR, a displacement was observed in the band at 1637 cm(-1), assigned to the amide I of the Nylon 6, to a higher wavenumber. This suggests a bigger interaction between the urethane group of the polyurethane and the amide group of the Nylon 6. Star block copolymers showed better mechanical properties compared with the linear ones. This behavior is attributed to the higher crystallinity and ramifications present in the materials. The structure and the thermal properties of the copolymers were studied using different techniques such as DSC, WAXS, DMA, and SEM. A decrease in the crystallinity when increasing the soft phase was also observed. Finally, physical tensile, impact, and hardness tests of the copolymers were carried out.