The title ligand, 5-methyl-3-formylpyrazole 4 N-benzylthiosemicarbazone (abbreviated as HMPzNB) has been synthesised and physicochemically characterised by elemental analysis, IR, PMR and mass spectrum. The ligational behaviour of the pyrazole-derived thiosemicarbazone, HMPzNB, has been examined by isolation and characterisation of its complexes with Co III , Ni II and Cu II with different counterions. Elemental analyses, magnetic and spectral features indicate [Co(MPzNB) 2 ]X (X = Cl - , Br - , NO - 3 , ClO - 4 or BF - 4 ) as the diamagnetic octahedral species with the ligand in the deprotonated thiol form, while [Ni(HMPzNB) 2 ]X 2 (X = Cl - , Br-, NO - 3 or ClO - 4 ) is proposed as octahedral complex with the ligand in the neutral thione form. However, in the neutral condition (pH ∼6) nickel(II) salt affords octahedral bis-nickel(II) complex, Ni(MPzNB) 2 , while copper(II) salt gives [Cu(MPzNB)]X (X = Cl - , Br - , NO - 3 or ClO - 4 ), with the deprotonated ligand. 5-Methyl-3-formylpyrazole 4N-benzylthiosemicarbazone possesses in its structure, the tertiary nitrogen atom ( 2 N) of the pyrazole ring, the azomethine nitrogen and the sulphur atom as potential binding sites; thus the title ligand is expected to behave as a potential NNS tridentate during complex formation with a metal ion.