1-benzoyl(1,2,4-triazol-3-yl)thiourea [BTThU] ligand and its [dimethyltin(IV), Pd(II) and Cu(II)] complexes are synthesized. The complexes are formed in molar ratio Cu(BTThU)₂, DMT(BTThU)₂ and Pd(BTThU)₂. The characterization has been done by using different physicochemical methods as elemental analyses, IR, ¹HNMR and molar conductance measurements. The stability constants of the formed species that produced from the interaction of [BTThU] with dimethyltin(IV) [DMT], dibutyltin(IV) [DBT] and diphenyltin(IV) [DPT] were determined potentiometrically using the non-linear least-square program MINIQUAD-75 in 50% ethanol–water mixture and 0.1M ionic strength at 25^oC. Concentration distribution diagrams for these system were evaluated. The theoretical conformational structure analyses were performed using density functional theory for thiol and thione tautomeric forms of [BTThU] ligand and its complex at B3LYP functional with 6-311G basis set for ligand and LANL2DZ basis set for complex. The theoretical vibrational frequency values of the optimized structures were calculated. The charge distribution within the ligand and its dimethyltin(IV) complex was calculated using Mulliken population analysis of [MPA] and natural population analysis [NPA]. The biological activity of BTThU ligand and its dimethyltin(IV) complex were tested in vitro against some selected species of fungi and bacteria. The hepatocellular antitumor effect of all compounds was investigated.