Since 1985, when Heyliger et al. first reported the in vivo insulin mimetic activity of oral vanadate, extensive studies exploring vanadium chemistry, including the synthesis of novel complexes and their biological effects both in vitro and in vivo have been pursued. Such complexes have emerged as possible potential agents for diabetes therapy. Among the several existing compounds, diketone based vanadium complexes have been chosen for the current study. Two new complexes namely bisdimethylmalonatooxovanadium(IV) and bisdiethylmalonatooxovanadium(IV) have been synthesized and characterized by UV-visible, FTIR and mass spectral studies. The antidiabetic activity of the complexes was proved by animal study. The results show that the above complexes have comparable antidiabetic potential with respect to the standard drug as well as with bisacetylacetonatooxovanadium(IV) which has been studied earlier by Reul et al. © 2008 Elsevier Masson SAS. All rights reserved.