A new mixed-chelate copper(II) complex with the general formula [Cu(Cl-acac)(diamine)]ClO4, where Cl-acac is 3-chloroacetylacetonate ion and diamine is N,N-dimethyl,N'-benzyl-1,2-diaminoethane, was prepared and characterized on the basis of elemental analysis, spectroscopic and conductance measurements. The mixed-chelate complex is soluble in various solvents and presents an interesting combination of solvato-and thermochromism. Its reversible chromotropism behavior is discussed in detail.