Three complexes of an ONS donor ligand of the Schiff base [C21H19NO2S] (HL), [Cu(C21H18NO2S)2] (1) [Co(C21H18NO2S)2] (2) and [Pd(C21H18NO2SCl)] (3), were synthesized and characterized by elemental analysis, FT-IR, 1H NMR, UV–Visible spectroscopy and single-crystal X-ray diffraction analysis. Single crystal X-ray diffraction analysis reveals that the copper complex acquires a distorted pyramidal structure and the palladium complex acquires a square planar structure. All the compounds are stable at room temperature and they show very good antibacterial activities against gram-positive and gram-negative bacteria. DNA binding activities of the ligand and its Cu(II), Pd(II) and Co(II) complexes with CT-DNA were carried out in DMF and tris-buffer (5 mM, pH 7.3) solution; all the three complexes along with the ligand show a very good intercalative mode of DNA interaction with Kb values of 1.56(±0.03) × 105 for 1 and 1.02(±0.09) × 105 for 3. The DNA binding activity has also been confirmed by a hydrodynamic study (viscosity). The order of DNA binding activity is 1 > 3 > 2.