The unique cage complexes [[(Me(4)en)Pd](3)-(L)(2)](X)(6) ( L = 1,3,5-tris(isonicotinoyloxyethyl)cyanurate; X- = BF4-, ClO4-) were constructed. A single water molecule in a skeletal cage was reversibly associated and dissociated via a combination of the adequate space, polar environment, and conformational flexibility of the cage. In Suzuki-Miyaura C-C cross-coupling reactions, the cage complex showed significant catalytic activity along with the effects of the isolated single water molecule.