The adsorption of mixed micelles of poly(4-(2-amino hydrochloride-ethylthio)-butylene)-blockpoly(ethylene oxide), PAETB(49)-b-PEO212 and poly(4-(2-sodium carboxylate-ethylthio)-butylene)-blockpoly(ethylene oxide), PCETB47-b-PEO212 on solid/liquid interfaces has been studied with light, X-ray, and neutron reflectometry. The structure of the adsorbed layer can be described with a two-layer model consisting of an inner layer formed by the coacervate of the polyelectrolyte blocks PAETB49 and PCETB47 (similar to 1 nm) and an outer layer of PEO212 blocks (similar to 6 nm). The micelles unfold upon adsorption forming a rather homogeneous flat layer that exposes its polyethylene oxide chains into the solution, thus rendering the surface antifouling after modification with the micelles.