The facile electron transfer catalysis of diaryl diselenides was utilized for the visible-light [4+2] homodimerization of decomposition-prone styrenes. The reaction required only 0.5 mol % TPT+BF4- photocatalyst and 1.5 mol % electron transfer catalyst (ArSe)2. The spontaneous electron transfer capability of diaryl diselenides was demonstrated for the first time, leading to the sequestration of redox-prone radical cation intermediates via electron transfer processes. A variety of polymerization-prone styrenes smoothly underwent the visible-light-promoted [4+2] homodimerization to tetralin derivatives.