Carbon-supported CoSe 2 nanoparticles, as non-precious metal cathodic catalyst, were prepared via the in situ surfactant-free method with the conventional heating. Structural and electrochemical properties of the obtained 20 wt.-% CoSe 2 /C nanoparticles were investigated by means of powder X-ray diffraction (PXRD), differential thermal gravimetric analysis (DTA-DTG) and rotating disc electrode (RDE) techniques. CoSe 2 nanoparticles have two kinds of crystal structure after heat treatment under nitrogen at different temperature: orthorhombic at 250 and 300 ยฐC; cubic at 400 and 430 ยฐC. The latter structure has higher oxygen reduction activity than the former in 0.5 M H 2 SO 4 . CoSe 2 /C nanoparticles after heat treatment from 250 to 430 ยฐC, have an onset potential from 0.78 to 0.81 V versus the reference hydrogen electrode (RHE) in O 2 -saturated 0.5 M H 2 SO 4 at 25 ยฐC. 20 wt.-% CoSe 2 /C nanoparticles, after heat treatment at 300 ยฐC, promote ca. 3.5 electrons, per oxygen molecule, transferred during the oxygen reduction process. They have an oxidation wave centred at 0.96 V versus RHE and display higher methanol tolerance as compared to 20 wt.-% Pt/C (E-TEK).