A series of 5,6-disubstituted pyridine-2,3-dione-3-thiosemicarbazone derivatives(2a-2n) and 5,6-disubstituted pyridine-2,3-dione S-benzyl-3-thiosemicarbazones(3a-3g) were synthesized starting from 2,3-dihydroxypyridine via oxidation-Michael additions, condensations and nucleophilic substitutions. The structures of the compounds were established by IR, (1)H NMR, (13)C NMR, and HRMS. All newly synthesized compounds were screened for their anticancer activity against Breast cancer (MCF-7), Colon cancer (HCT-116) and hepatocellular cancer (BEL7402) cell lines. Bioassay results indicated that most of the prepared compounds exhibited cytotoxicity against various cancer cells in vitro. Some of the compounds exhibited promising antiproliferative activity, which were comparable to the positive control (5-fluorouracil). The structure-activity relationship was discussed.