New supported catalytic systems based on the immobilization of a ligand onto supported (co)polymers were prepared, allowing copper immobilization onto a solid support during the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). The supported catalysts were elaborated by the ATRP of 2-vinyl-4,4-dimethyl-5-oxazolone and/or styrene onto a Wang resin initiator. The best results were obtained with the supported ATRP of styrene followed by the nucleophilic substitution of bromine by N,N,N′,N′-tetraethyldiethylenetriamine (Wang-g-polystyrene–N,N,N′,N′-tetraethyldiethylenetriamine) at the chain end of the grafted polystyrene chains. The supported complexes mediated a controlled polymerization of MMA, yielding polymers with controlled molar masses and low polydispersity indices. Moreover, after the polymerization, 96% of the initial copper was kept in the beads.