Multiwalled carbon nanotube/poly(m-phenylene isophthalamide) (MWNT/PMIA) nanofibers mats with different MWNT contents were successfully prepared by electrospinning. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD) and a thermal gravimetric analyzer (TGA) were used to characterize the morphology and properties of nanofibers. The results showed that the nanofiber diameter is reduced with increasing MWNT concentrations and the surfaces of the MWNT/PMIA nanofibers becomes rough compared with those of the virgin version. The MWNTs are well dispersed in the nanofibers and well-aligned along the nanofibers. The dosing level of MWNTs seems to show only minor influences on both the crystalline structure and the initial degradation temperature of the nanofibers. While the mechanical properties of the nanofiber mats are generally improved with the addition of MWNTs. The striking improvement occurs at the loading of 0.6 wt% with the increase of tensile strength at breakage by ca. 86%.