Abstract: Trifluoromethylation-based difunctionalization of alkenes provides a step-economical route to CF3-containing polyfunctionalized organics. New and scalable process is highly desired in this field. Here, we report a simple and environmentally benign method for olefinic thiocyanotrifluoromethylation. By the use of PhICF3Cl as unique CF3 agent and NaSCN as the SCN source, the difunctionalization of alkenes selectively occurs on water at ambient condition. Mechanism studies suggest a radical process in which SCN anion is proposed to act as not only reductive initiator but also S-nucleophile. All tested reactions are compatible with mono-, di-, tri-, and tetra-substituted alkenes and with high functional group tolerance. This method is also suitable for the selenocyanotrifluoromethylation of alkenes. Therefore, a sustainable platform has been established to synthesize valuable β-trifluoromethylated thio(seleno)cyanates in green way. Keywords: Alkenes; Difunctionalization; Radical addition; Thiocyanotrifluoromethylation; On water