The 2-phenylphthalazinone derivatives are the main skeleton of various pharmaceuticals. In this work, an efficient method for the regioselective Ru(II)-organometallic complex-catalyzed alkenylation of 2-phenylphthalazinone through N-directing group via C–H activation process is presented. The results have proved to be satisfactory for a wide range of yields bearing an electron-donating and electron-withdrawing groups on substrates.