This paper extended the authors previous work of demonstrating the concept of polymer nanofiber interleaving to enhance the toughness of fiber reinforced carbon/epoxy composite laminates. In this study, in-plane tension, compression, interlaminar shear, and Mode I fracture and fatigue onset life properties were studied. Results demonstrated that by adding 1% weight of nanofibers in the form of interlayer in-plane tension and compression properties (strength, modulus, and Poisson’s ratio) of interleaved composites remained the same as base composites. Whereas polymer nanofiber interleaving increased interlaminar shear strength by 4%, fracture toughness by 150% and fatigue threshold energy release rate by 67%