Clitoria ternatea is a native plant with medicinal and nutritive significance in Asia. The goal of this work was to examine the antiproliferative role of Clitoria ternatea against colorectal (HCT116), breast (MCF-7), and thyroid (TT) cancer cell lines at cellular and molecular levels. A phytochemical analysis, the cytotoxic effect, an apoptotic induction cell cycle analysis, and the expression level of GAX, DIABLO, and NAIP1 genes were assessed. The plant extract exhibited a clear cytotoxic action against the utilized cancer cell lines via a low IC50, foremost by means of cell cycle arrest at the pre-G0, G1, and S phases associated with an apoptotic induction. An apparent raise in the mRNA levels of GAX and DIABLO and a concomitant decrease in the NAIP1 mRNA level were observed in the used cancer cells treated with the IC50 of the plant extract. This study concluded that an ethanolic extract of Clitoria ternatea induced apoptotic cell death, suggesting that it could possibly be utilized as a new source of an apoptosis-inducing anticancer agent for colon, breast, and medullary thyroid cancer cell line treatments with further detailed studies.