Zinc(II) complexes with a Zn(O-4) coordination mode were found to have insulinomimetic activity. A bis-maltolato zinc(II) (Zn(Mal)(2)) complex was revealed to be in an octahedral and a square pyramidal geometries in a unit fell. Both Zn(Mal)(2) (IC50 = 0.59 mM) and bis-2-hydroxypyridine-N-oxide zinc(II) (IC50 = 0.41 mM) complexes exhibited higher insulinomimetic activity than VOSO4(IC50 = 1.00 mM) and ZnSO4(IC50 = 0.81 mM) in terms of IC50 values, which show 50% inhibition concentration of the complex in the free fatty acids release from rat adipocytes.