Oxazoline functionality is well known to be highly reactive toward a lot of other functional groups like carboxyls, hydroxyls, mercaptans, and amines. In this work we report the possibility to modify the nitrile groups of an acrylonitrile/butadiene/ styrene (ABS) copolymer into oxazoline in the molten state in the presence of amino-ethanol as modifier agent and zinc acetate as a catalyst. The reaction has been carried out in a batch mixer and in a corotating twin screw extruder. The conversion of the nitrile groups into oxazoline has been verified by infrared spectroscopy, NMR analysis microanalysis and confirmed by thermomechanical characterization. The results indicate that the kinetic of grafting is fast and the conversion of the nitrile groups into oxazoline relatively high, encouraging the use of this modified polymer in the reactive compatibilization of ABS-based blends.