A new pyrazole based ‘NNS’ tridentate ligand, 5-methylpyrazole-3yl-N-(2′-methylthiophenyl)methyleneimine (MPzOATA), has been synthesized and characterized by elemental analyses, mass, IR and NMR spectroscopy. The versatile coordination mode of the ligand has been established with the synthesis of two metal–organic complexes with different metal ions, Co(III) (complex I) and Cu(II) (complex II). These metal–organic complexes have been characterized by single crystal X-ray structure analyses, along with several spectral techniques. Structural analyses of both the monomeric complexes reveal that complex I crystallized in the monoclinic C2/c space group, while complex II crystallized in the orthorhombic Pbca (#61) space group. In complex I, the Co(III) centre shows a six coordinate octahedral geometry, while in complex II, the Cu(II) centre shows a five coordinate square pyramidal geometry. The reported ligand and the metal ion complexes have been screened for their in vitro antimicrobial activity against some pathogenic bacteria.