Anion Exchange Membrane Fuel Cells (AEMFCs) are a promising alternative for sustainable and clean energy generation. However, their large-scale production is limited by the scare noble-metal catalysis availability. In this regard, the development of metal-free electrocatalysts is a feasible option for the large-scale commercialization of AEMFCs. In this work, dual heteroatom-doped carbon nanofibers (CNFs) have been synthetized by electrospinning technique and subsequent thermal treatments. Polyvinylpirrolidone (PVP) and Dimethyl Sulfoxide (DMSO) have been used as nitrogen and sulfur precursors, respectively. The physicochemical properties have been determined by Field-Emission Scanning Electron Microscopy (FESEM), Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. The results indicate that dual heteroatom-doped carbon nanofibers are obtained (diameter ≈ 350 nm) and the formation of species of N-species (i.e., N-pyridinic, N-pyrrolic and N-graphitic) and S-species (i.e., thiophene and oxidized-S) on the surfaces of the N-S-doped CNFs is confirmed. Moreover, the catalytic activity for the oxygen reduction reaction (ORR) is evaluated by Rotating Ring-disc Electrode (RRDE) technique in alkaline electrolyte (0.5M KOH). The most active metal-free electrocatalyst labelled as S-CNF has an onset potential of 0.817 V vs. RHE, HO₂^- % yield of ≈12-15% and n = 3.7 and high ethanol tolerance. In addition, the Accelerated Degradation Test (ADT) show that the S-CNF catalytic activity decrease only 13% evaluated at a potential range of 0.6 to 1.0 V vs. RHE during 3000 cycles at scan rate of 50 mVs^-1. Furthermore, S-CNF metal-free electrocatalyst even is evaluated by ADT as support (1.0 to 1.6 V/RHE, 6000 cycles, 50 mV s^-1) showing high long-term stability decreasing only 11% its catalytic activity. These results indicates that electrospun N-S-codoped CNFs are a promising, scalable, and eco-friendly alternative for the generation of metal-free electrocatalysts toward the ORR.