With the aim of obtaining a highly stable and active catalyst for oxygen evolution reaction (OER), a core–shell-like IrO2@RuO2material was synthesized by using a surface modification/precipitation method in ethanol medium. The comparison of this catalyst with pure RuO2and pure IrO2showed that the obtained mixed oxide catalyst displayed the highest amount of active sites as well as a good accessibility for water. Moreover, this catalyst was shown to be highly stable toward repetitive redox cycling. Polarization curves of the three catalysts showed that the IrO2@RuO2was the most active for the OER due to the large number and high accessibility of active sites. These catalytic benefic effects are attributed to an intimate contact between the two oxides in the IrO2-covered RuO2nanocatalyst that combines the RuO2intrinsic activity and the IrO2stability. The present study contributes therefore to the rational design of efficient and stable electrocatalysts for water splitting in acidic media.