A number of novel di- and triorganotin(IV) complexes1–5(Ph2SnL1, Ph2SnL2, Et2SnL2, Ph3SnL3, Ph3SnL4) with mono- or dianionic forms of thio-Schiff bases containing antioxidant sterically hindered phenol or catechol fragments were synthesized. Compounds1–5were characterized by1H,13C NMR, IR spectroscopy, and elemental analysis. The molecular structures of complexes1and2in the crystal state were established by single-crystal X-ray analysis. The antioxidant activity of new complexes as radical scavengers was estimated in DPPH and ABTS assays. It was found that compounds4and5with free phenol or catechol fragments are more active in these tests than complexes1–3with tridentate O,N,S-coordinated ligands. The effect of compounds1–5on the promoted oxidative damage of the DNA by 2,2’-azobis(2-amidinopropane) dihydrochloride and in the process of rat liver (Wistar) homogenate lipid peroxidation in vitro was determined. Complexes4and5were characterized by more pronounced antioxidant activity in the reaction of lipid peroxidation in vitro than compounds1–3. The antiproliferative activity of compounds1–5was investigated against MCF-7, HTC-116, and A-549 cell lines by an MTT test. The values of IC50are significantly affected by the presence of free antioxidant fragments and the coordination site for binding.