The CuII complex bis[hydroxybis(pyridin-2-yl)methanesulfonato-κ3 N, O, N′]copper(II) hexahydrate, [Cu(C11H9N2O4S)2]·6H2O, (I), crystallizes in the space group P, compared with P21/ c for the anhydrous CoII analogue bis[hydroxybis(pyridin-2-yl)methanesulfonato-κ3 N, O, N′]cobalt(II), [Co(C11H9N2O4S)2], (II). However, both molecules sit on a crystallographic inversion centre and are thus very similar in appearance. Jahn-Teller elongation of the Cu-O bonds [2.347 (3) Å in (I) and 2.064 (2) Å in (II)] influences the S-O bond lengths, which are all around 1.455 (3) Å in (I) and 1.436 (2)-1.473 (2) Å in (II). [ABSTRACT FROM AUTHOR]