Abstract This chapter deals with the influence of different types of fillers such as macrofillers, microfillers, and nanofillers on the material properties of polyurethane (PU) composites and nanocomposites. The PU composites and nanocomposites based on different suitable fillers have received remarkable attention from academicians, researchers, and industrial personnel, since their early research and development stages. Nowadays, various filler-based PU composites and nanocomposites play a crucial rule in view of their noticeable performance properties and multifunctional applications. PU is an important synthetic polymer because of its good mechanical properties, excellent transparency, high abrasion resistance, excellent shock absorption, good flexibility, high elasticity, good low-temperature performance, and outstanding oil and grease resistance, and many more. The reinforcement of fillers into the PU matrix significantly increases the overall properties of the composites and nanocomposites due to the synergism between the counterparts. The shape (spherical, blucky, platy, fibrous, tubular, irregular, etc.), size (macro, micro, and nano), and dimensions (1D, 2D, and 3D) of the fillers are the vital controlling factors to select a proficient competent one. The effective uniform dispersion of fillers within the PU matrix as well as the development of strong interfacial interactions among PU matrix and fillers to institute a successful interphase load transfer mechanism, are the important factors for preparation of superior filler-reinforced PU composites and nanocomposites.