We studied a dissolved oxygen sensor in aqueous media based on a mesoporous Pt microelectrode with the aim of obtaining a large sensor output. Mesoporous Pt structures were fabricated via Pt thin film deposition on a skeleton of nanoporous gold. The dissolved oxygen was measured via adoptive stripping voltammetry, i.e., the dissolved oxygen was adsorped on the surface of the mesostructured platinum microelectrode over a certain period. Accumulated oxygen on the surface of the mesostructures was reduced through voltammetry with a large current. This led to a linear increase in the reduction current as a function of the active surface area of the Pt mesostructures, indicating that the entire surface area of the mesostructures is utilized to adsorb and reduce oxygen in the given experimental condition. The proposed method could obtain a lager sensor output compared with sensors under diffusion-controlled reactions and better fits for oxygen sensors in micro total analysis systems. (c) 2019 The Electrochemical Society.