An efficient, amine- and phosphine-free palladium(II)-catalyzed homocoupling of terminal alkynes has been developed. In the presence of PdCl 2 , CuI, Me 3 NO, and NaOAc, homocoupling of various terminal alkynes underwent smoothly to afford the corresponding diynes in moderate to high yields without any phosphine ligands. In contrast, the presence of a phosphine ligand (PPh 3 ) disfavored this palladium-catalyzed homocoupling procedure. Bases, solvents, and CuI have fundamental influence on the palladium-catalyzed homocoupling of terminal alkynes.