A new series of 3-allylthio-6-(mono or disubstituted) aminopyridazines was synthesized by reacting 3-allylthio-6-chloropyridazine with several amines to develop new anticancer agents. These new compounds showed antiproliferative activities against lung cancer (A549), hepatoblastoma (Hep3b), prostate cancer (PC3), colon cancer (SW480) and cervical cancer (HeLa) cells in MTT assays, and could be promising candidates for chemotherapy of carcinomas. Compound 5 (3-allylthio-6-homopiperidinylaminopyridazine) showed higher potencies than 5-FU for inhibiting the growth of these cell lines. This suggests the potential anticancer activity of compound 5.