In view of producing environmentally friendly materials without compromising the properties, new composites containing polylactic acid as matrix and chitosan, with or without keratin fibers have been obtained. The morphological, mechanical, rheological, and thermal characterizations of the composites were performed before and after accelerating weathering. In normal conditions, the presence of keratin improved the toughness and thermal stability of polylactic acid (PLA)/chitosan material. Upon accelerated weathering, thermal degradation of the PLA matrix was faster in the presence of chitosan, as compared to the composite containing chitosan and keratin. Fractured surfaces of the exposed composites are rougher related to the unexposed samples, as revealed by SEM. XRD analysis recorded selective degradation of the amorphous part of the materials. The decrease of the complex viscosity values after UV exposure of the blends indicated that chain scission was the most prominent phenomenon in accelerated weathering tests.