Polyamides, obtained from step-growth polymerization between dicarboxylic acid and diamine, are very important polymers used in many different industrial applications. In addition to the many advantages typical of this class of polymers, among them high mechanical performances together with chemical and thermal tolerance, the absence of moisture absorption is one the main drawbacks that reduces their application. In this work, we functionalized nylon-6,6 with polyetheramine using reactive extrusion, which allows for proper reaction conditions without initiators, catalysts, or organic solvents. Fibers obtained were characterized using nuclear magnetic resonance, Fourier-transform infrared spectroscopy, differential scanning microscopy, and scanning electron microscopy. The final hydrophilicity was checked with contact angle measurements and X-ray diffraction then compared with nylon-6,6 fibers. We discovered that this modification influences also the antibacterial activity of the fibers that was studied and clearly demonstrated against Staphyloccoccus aureus and Klebsiella pneumoniae, two well-known opportunistic pathogens. The possibility to obtain a functionalized polymer that is able to maintain the high performance of nylon-6,6 together with higher hydrophilicity and antibacterial activity may pave the way to the use of this polyamide in many other industrial applications.