We report a novel and highly selective electrochemical method for the synthesis of β-iodoesters via difunctionalization of alkenes. The reaction is carried out in an undivided cell under constant current conditions without any additives, catalysts, oxidants, and sacrificial reagents. Inexpensive and readily available tetrabutylammonium iodide not only acts as an electrolyte but also serves as an iodine source. The reaction shows high selectivity and good functional group tolerance, providing products in yields of up to 98%. This method is applicable not only to the iodofunctionalization of alkenes but also to the chloro- and bromofunctionalization of alkenes. The successful modification of drugs and natural products demonstrates the potential utility of this approach.