The Schiff base ligand (L) N-(4-(diethylamino-2-hydroxybenzylidene)isonicotinohydrazid was synthesized by reaction of isoniazid with 4-(diethylamino)-2-hydroxybenzaldehyde using microwave assisted method and then synthesized its transition metal complexes having general formula [Cr(L)₂], [Mn(L)₂], [Fe(L)₂], [Co(L)₂], [Ni((L)₂], [Cu((L)₂] and [Zn(L)Cl]. ¹H NMR, ¹³C NMR, FT-IR and TGA characterized the synthesized Schiff base and its transition metal complexes. Spectroscopic data indicate that the Schiff base ligand (L) is tridentate, featuring an ONO donor atom. The synthesized Schiff base transition metal complex [Zn(L)Cl] demonstrated the highest antidiabetic inhibitory activity with 50% inhibition, whereas the other complexes showed a maximum inhibition of 30%. The synthesized Schiff base and its transition metal complexes do not exhibit fluorescence.