Cu(II), Fe(III), and Mn(II) complexes of a novel ligand N′-[(4-methoxy)thiobenzoyl]benzoic acid hydrazide (H 2 mtbh) have been synthesized and characterized by elemental analyses, IR, UV–vis, NMR, mass, EPR and Mössbauer spectroscopy. The results suggest a square planar structure for [Cu(Hmtbh)Cl] and [Cu(mtbh)] whereas an octahedral structure for [Mn(Hmtbh) 2 ] and [Fe(Hmtbh)(mtbh)]. Mn(II) and Fe(III) complexes were found to inhibit proliferation of HT29 cells. [Mn(Hmtbh) 2 ] and [Fe(Hmtbh)(mtbh)] inhibited proliferation of HT29 cells with half maximal inhibition (IC 50 ) of 8.15±0.87 and 68.1±4.8μM, respectively, whereas H 2 mtbh showed growth inhibition with IC 50 of 90.9±7.8μM and were able to inhibit NMT activity in vitro. Mn(II) and Fe(III) complexes inhibited NMT activity in a dose dependent manner with IC 50 values of 20±2.2 and 60±7.2μM, respectively, whereas ligand (H 2 mtbh) displayed IC 50 of 3.2±0.5mM.