This chapter will present an introduction to a novel class of multifunctional scale-bridging materials known as fuzzy fibers, which consist of multi-walled carbon nanotubes grown directly on the surface of structural carbon and glass fibers. The chapter will then identify some of the key challenges in the modeling of the mechanical, electrical, and thermal properties of fuzzy fibers and the composites in which they are embedded, and review some of the recent efforts to model these materials available in the literature. Finally, the description and a demonstration of the application of analytic composite cylinders model and computational homogenization approaches to modeling fuzzy fibers will be provided. A discussion of the potential applications for fuzzy fibers will close the chapter. © Springer International Publishing Switzerland 2014.