Simultaneous redox free radical polymerization (FRP) and redox cationic polymerization (CP) are combined for the synthesis of methacrylate/diepoxide interpenetrating polymer networks (IPN). At first, the Cu­(acac)2/phosphine/iodonium salt operates according to the principles of free radical promoted cationic polymerization (FRPCP). A photoactivation of the reaction for that system was necessary to enhance the mild methacrylate and diepoxide conversions. Second and at least, two complementary copper catalytic cycles are used simultaneously: the recently developed Cu­(II)/reducing agent/peroxide FRP system combined with the older Cu­(II)/reducing agent/iodonium salt redox CP system. For this latter hybrid system, outstanding efficiency was observed with more than 90% of epoxy functions conversion for the cationic difunctional monomers and 78% conversion for the vinylic functions conversion for difunctional monomers. The radical and cation generations are discussed in order to fill the interrogations raised by the experimental results. The relevance of dual FRP/CP in IPN synthesis is fully demonstrated. The performance of the hybrid copper catalytic system is remarkable to overcome the oxygen inhibition; i.e., almost no oxygen inhibited layers are observed compared to the >60 μm inhibited layer obtained with a reference redox FRP such as amine/BPO.