A series of novel indolylquinones have been synthesized by treating halogeno-quinone with 2-substituated indole derivatives in the presence of kalium carbonate and TEBA in acetonitrile at room temperature. These compounds were evaluated for their antiproliferative activity against human MDA-MB-231 and MCF-7 breast cancer cell lines. All the tested compounds showed potent mircomolar cytotoxicity activity in both breast cancer cell lines. 3d (IC(50) value=2.29 μg/mL for MCF-7 cells) and 3g (IC(50) value=3.99 μg/mL for MDA-MB-231 cells) displayed the most potent antiproliferative activity of the series. Also, in vitro anticancer activity of the compounds further showed that bis-indolylquinones were more active than mono-indolylquinones. Fluorescence microscopy analysis indicated that compound 3d and 3g inhibited breast cancer cells proliferation by triggering apoptotic cell death.