The relevance of this study is determined by the increasing practical importance of thiosemicarbazones, which are used as medicaments. However, at the same time there is no systematic information about the features of their structure and the effect of the structure on biological activity. The aim of this work is the synthesis, determination of the composition, structure, physicochemical and antitumor properties of methyl N-prop-2-en-1-yl-N'(pyridin-2-ylmethylidene)carbamohydrazonothioate (HL) as well as iron(III), cobalt(III), nickel(II), and copper(II) coordination compounds with this ligand.CH2 CH CH2 NH C N S N N CH CH3 HL For achieving these objectives 4-allylthiosemicarbazide was alkylated with iodomethane. After that, the 2-formylpyridine was added to the reaction medium. The resulting hydroiodide of 4-allyl-S-methylisothiosemicarbazone was neutralized with sodium carbonate. The purity of HL was proved by NMR (1H, 13C) and IR spectroscopies. The experiments showed that ethanolic solutions of copper, nickel, cobalt and iron salts react with synthesized methyl N-prop-2-en-1-yl-N'-(pyridin-2ylmethylidene)carbamohydrazonothioate in 1:1 molar ratio in case of copper and nickel salts, or 1:2 molar ratio in case of other metals forming fine-crystalline colored coordination compounds. The composition, structure of the coordination compounds and the way of ligand coordination were determined on the basis of data from elemental analysis, magnetochemical research, IR spectroscopy, and X-ray diffraction analysis. The elemental analyses on iron, cobalt, nickel, copper and gravimetric analysis of water content indicate the general formulae Me(HL)X·nH2O (Me= Cu2+, Ni2+; X=Cl-, Br-, I-, NO3-, ClO4-; n=0-2) and Me(L)2X (Me= Co3+, Fe3+; X=Cl-, NO3-). The study of antitumor activity showed that synthesized substances inhibit proliferation of the human leukemia HL-60 and cervical cancer HeLa cells at 10 μM and 1μM. It was established that free ligand manifests biological activity only in case of HeLa cells.