Hydrophosphination of 1-alkynylphosphines with diphenylphosphine proceeds in an anti fashion under copper catalysis, providing an easy and efficient access to a variety of (Z)-1,2-diphosphino-1-alkenes and their sulfides. The reaction is highly chemoselective and can be performed even in an aqueous medium. The reaction is reliable enough to realize a gram-scale synthesis of (Z)-1,2-diphosphino-1-alkene. Radical reduction of the diphosphine disulfides with tris(trimethylsilyl)silane yields the parent trivalent diphosphines without suffering from the isomerization of the olefinic geometry. Enantioselective hydrogenation of (Z)-3,3-dimethyl-1,2-bis(diphenylthiophosphinyl)-1-butene followed by desulfidation leads to a new chiral bidentate phosphine ligand.