Exploration of oxygen reduction reaction (ORR) catalysts based on non-precious metals is of great importance to the development of fuel cells. In this work, we theoretically investigate the practical feasibility and catalytic activity of two-dimensional (2D) group IVA monochalcogenides MXs (M = Ge/Sn and X = S/Se) as potential and efficient ORR catalysts. Through first-principles calculations, it is found that these 2D MXs are semiconductors with high adsorption affinity and dissociation activity for oxygen molecules. Furthermore, the free energy diagrams along the four-electron pathway are simulated to elucidate the whole ORR mechanism catalyzed by the monolayer MXs (GeS, GeSe, and SnSe here), with all the energetically favorable intermediates being exothermic in free energy. In the acidic environment, the GeS monolayer exhibits the best performance due to its considerably low overpotential (0.52 V). While in the alkaline environment, there is no overpotential for the ORR catalyzed by the 2D MXs (GeS, GeSe, and SnSe). Our work provides a novel insight into the electrochemical applications of IVA monochalcogenides, which is expected to realize experimentally.