Complexation of cyclohexanocucurbit[6]uril (Q(star)[6]), a water-soluble cucurbit[n]uril derivative, with Cd2+ ions has been studied by means of cyclic voltammetry and differential pulse voltammetry. The electrochemical experimental data prove the formation of a highly stable 1:6 Q(star)[6]/Cd2+ complex. We also obtained the single-crystal X-ray structure of a cadmium ion complex with Q(star)[6], in which each portal of Q(star)[6] chelates three cadmium ions. The present study suggests the potential utility of O-star[6] as an effective cadmium ion chelator and extractant.