Arylation of tertiary aryl and alkyl phosphines bearing 2‐cyanoethyl group with aryl(mesityl)iodonium triflates under blue light irradiation followed by retro‐Michael reaction of the in situ generated quaternary phosphonium salts initiated by DBU represent a novel efficient and general method for the preparation of distinctly substituted tertiary arylphosphines. An operationally simple, one‐pot protocol features mild, transition‐metal‐free conditions, high selectivity, broad functional group compatibility, as well as scalability and would be applied to substrates with different electronic and steric nature.