The oxygen reduction reaction (ORR) is the key half-reaction in various modern transduction devices. However, it is still hugely urgent to exploit high-efficiency and low-cost catalysts to overcome the problem of the slow dynamics for the ORR. Here, a catalyst with atomic Sn centers decorated into N-doped porous carbon, namely Sn–NC, was formulated by thermal decomposition of SnCl₂ and laver in the presence of ZnCl₂. Electron microscopy and X-ray absorption spectroscopy demonstrate the atomic distribution nature of Sn species in Sn–NC with a SnN₄ coordination structure. Impressively, Sn–NC displays superior ORR activity in both acid and alkaline solutions with a half-wave potential of 0.98 V versus reversible hydrogen electrode (RHE) in 0.1 M KOH and 0.82 V versus RHE in 0.1 M HClO₄ as well as good stability. More importantly, when employed as the cathodic active material of a Zn–air battery and fuel cell, Sn–NC shows a peak power density of 118 and 1290 mW cm⁻², respectively, competitive to the commercial Pt/C catalyst. This work should be helpful for exploiting inexpensive ORR catalysts with promising potential for practical application.