Title compound, [C11H19CuN4O2+]2·(ClO4)2·(H2O), is a dimmer with two copper atoms of asymmetric unit bridged together by an oxime oxygen of the adjacent unit. In each unit the copper atom is coordinated to a tetradentate ligand through the two oxime and two imine nitrogen atoms. The water molecule also coordinated weakly to apical position of each copper atom.