Depending on processing, different polyamide types are required. While in injection molding polyamide (PA) with low viscosities is used, higher viscosities are required for extrusion or thermoforming. In order to increase the molar mass and hence the viscosity of PA, the solid state polycondensation is used, which is however time-consuming and thus expensive. An alternative method is reactive extrusion. In doing so, so-called chain extend-ers are added during compounding and thus simultaneously to the metering of further additives. In this work, PA6 modified with different chain extenders are compared. The different chain extenders either connect polymer chains linearly or act as a backbone with grafted chains. The compounding is carried out in a twin-screw extruder. The changes in the viscosity are examined by means of plate-plate rheometer and those of molar mass by means of gel permeation chromatography (GPC). In addition, the influence on the mechanical properties is tested. It can be shown that a significant increase in the viscosity due to the chain extension occurs. The meas-urements of the GPC confirm the increase of the molar mass, whereby even a bimodal distribution of the molar mass occurs due to grafting. The reactive extrusion is thus a cost-effective alternative to increase the viscosity of PA6 and thereby to increase its range of applications.