In this study, the polyurethane (PU) nanofibers mat produced by electrospinning method was used as filler in the polymer composites; fiberglass (FG) and carbon fiber (CF) were employed as reinforcement materials. Moreover, their mechanical properties were compared to sepiolite and SiO2 powder reinforced composites. The mechanical properties of composites were evaluated using tensile and flexural tests. Moreover, the morphology of composite was assessed by microscopy techniques. The findings show that the nanofiber-doped FG and CF composite had at least 30% higher tensile strength compared to unreinforced and rival composites; the tensile strength was 135 MPa for FG-Nanofibers and 134 MPa for CF-Nanofibers. On the other hand, the flexural analysis showed that the powders filler had poor flexural stress against untreated composite. However, the flexural strength of FGNanofibers and CF-Nanofibers reached 197 MPa and 553 MPa, respectively. The better mechanical properties of nanofiber doped composites were due principally to the random distribution of nanofibers which support all loads from different directions. The crosssection analysis of composites demonstrated that the powders were distributed heterogeneously and some agglomeration was observed at some locations. Generally speaking, it can be concluded that the addition of PU nanofibers increased the mechanical properties of composites, and the tensile strength was at least 3 times higher for CF composites compared to untreated composite.