A new series of bis(aryl or aralkyl) diselenides 5a-5q was synthesized by selenylation from aryl halide (or aralkyl halide) for development of new anticancer agents. The process involves the reaction of aryl halides (or aralkyl halides) with selenium, hydrazine hydrate under atmospheric pressure in the presence of sodium hydroxide, to afford diorganodiselenides. These new compounds showed antiproliferative activities against breast cancer (MCF-7) cells in CCK-8 assays, and could be promising candidates for chemotherapy of carcinomas. Among 17 synthesized compounds for inhibiting the growth of these cell lines, 1,2-bis(chloropyridazinyl) diselenide 5a showed the highest potency. This result suggests the potential anticancer activity of compound 5a.