A chain-extender based on 1,1-Carbonyl-Bis-Caprolactam (CBC) was melt compounded with a commercial Polyamide 6 (PA6) by using a twin screw extruder. Rheological, thermal, and mechanical tests were performed on the resulting materials to evaluate the chain extension capability of CBC. Rheological tests on the compounded pellets and relative viscosity measurements on solubilized samples evidenced an increase of the viscosity values with the chain-extender amount, while the opposite trend was determined increasing the high temperature residence time. Terminal group analysis confirmed the increase of the molecular weight with the CBC content and highlighted a preferential reactivity of the chain-extender with aminic end groups. Differential scanning calorimetry (DSC) tests showed how both melting and relative crystallinity of the up-graded samples decreased with the CBC amount. Elastic and yield properties of chain-extended PA6 were similar to those of neat PA6 grades at different molecular weight, while crystallinity drop due to chain extension was responsible of an increase of the strain at break values. POLYM. ENG. SCI., 54:158-165, 2014. (c) 2013 Society of Plastics Engineers