A method to reduce noble metal content in oxygen-evolving electrocatalysts suitable to work in acidic media is presented. TiO2-RuO2 anodes can be promoted by Mn, resulting in increased activity and stability. The most active composition displayed an overpotential of 386 mV at a current density of 10 mA cm–2, and a Tafel slope of 50 mV dec–1. This anode only included 17 at% Ru out of the total amount of metals included in the film. We investigated the influence of Mn addition to TiO2-RuO2 on the structure, morphology, and surface area, and related differences to catalytic activity and stability. We found that increased porosity of the anode film by Mn addition and Mn inclusion in the TiO2-RuO2 lattice can explain the enhanced catalytic activity. A detailed characterization of fresh and used anodes provided insight into structural modifications induced by electrochemical treatment.