The number of worldwide patients suffering from diabetes mellitus (DM) is forecasted to increase over time. The development of compounds without severe side effects for type 2 DM is required not only to treat DM but also to improve the quality of life (QOL) of patients. In this paper, we have described the synthesis of novel first transition metal complexes with S2O2 coordination mode and discussed their anti-diabetic activities. Di(1-oxy-2-pyridinethiolato)Zn complex (Zn(opt)2) with Zn(S2O2) coordination mode displayed higher insulin mimetic with anti-diabetic activity, compared to the ZnCl2 or clinically used medicine (pioglitazone). In addition, Zn(opt)2 improved the insulin and adiponectine levels in the plasma. The gastrointestinal absorption of the Zn complex was found to be higher than that of ZnCl(2). Based on these results, we propose that the Zn(opt)2 complex with Zn(S2O2) coordination mode is a novel candidate for the treatment of type 2 DM; through oral administration.