Furane- and thiophene-2-earboxylaldehyde undergo condensation reaction with 2­aminothiazole to give tridentate NNO and NNS Schiff base ligands, respectively. The synthesized Schiff base ligands have been further used for their complexation reaction with Co(II) and Ni(II) having the same metal ion (cation) but different anions. Structural elucidation of these Schiff base ligands and its metal complexes having the same metal ion (cation) but different anions, [NO3-, SO42- C2O42- or CH3CO2] have been done on the basis of their physical, analytical and spectral data. In order the evaluate the effect of anions, these compounds have also been screened for their varied antibacterial actively against bacterial species, Escherichia coli. Staphylococcus aureous and Pseudomonas aeruginosa