Developing active and durable metal-free oxygen reduction reaction (ORR) electrocatalysts is central to reducing cathode cost and improving the operational stability of anion-exchange membrane fuel cells (AEMFCs). Here, P,S-modified g-C3N4 was pyrolyzed on acid-treated multi-walled carbon nanotubes (MWCNTs) to form an N,P,S-doped porous carbon layer integrated with a conductive nanotube network. Among the investigated precursor ratios and pyrolysis temperatures, P,S,N-C/CNT(1:2)@800 exhibited the highest ORR activity, with an onset potential of 0.97 V, a half-wave potential of 0.82 V, and a limiting current density of 5.98 mA cm−2 in O2-saturated 0.1 M KOH. Koutecky-Levich analysis yielded an apparent electron-transfer number of approximately 3.9, indicating a predominantly four-electron ORR pathway, while the polarization response was largely retained after 15,000 potential cycles. In an H2/O2 AEMFC, the catalyst delivered a peak power density of 568 mW cm−2, exceeding the 445 mW cm−2 obtained with the Pt/C cathode under the same cell configuration. During constant-current operation at 0.2 A cm−2, the P,S,N-C/CNT(1:2)@800 cell showed a voltage loss of only 8.8%, lower than the 14.1% loss measured for Pt/C. These results demonstrate that the g-C3N4-derived N,P,S-doped carbon/MWCNT hybrid is a promising metal-free cathode catalyst for alkaline fuel-cell applications.