Poly(methyl methacrylate) composites reinforced with natural protein biofibers from chicken feathers were prepared and evaluated through a series of tensile tests. Afterward, the samples were analyzed by optical and scanning electron microscopy studies, to obtain a clear picture of the tensile-induced damages. The hydrophobic nature of keratin fiber produces an excellent compatibility between fibers and PMMA matrix. This fact is reflected in the good dispersion of protein fibers achieved without use of coupling agents. The normally rigid behavior of PMMA may be modified by using keratin fibers as were demonstrated by tensile test; while at the same time, Young's modulus of composite material is also increased. The microscopic studies realized at the corresponding fracture surface level show good adherence between fibers and matrix. These results demonstrate that feather fibers could be a new source of natural high structure fibers useful to create new materials provided with satisfactory properties. (c) 2005 Published by Elsevier Ltd.