© 2015 Elsevier B.V. Acalypha californica Benth., is a plant in the northwestern region from Mexico, commonly known as "cancer herb" and used in traditional medicine for treating cancer. In the present study we have investigated the antiproliferative activity of methanolic extract of A. californica and its fractions in cancer cell lines and phytochemical analysis and mechanism of apoptosis of the fractions with antiproliferative activity. The antiproliferative activity of methanol extract and its fractions of solvents were evaluated by MTT assay against the M12.Ak.C3.F6, RAW 264.7, HeLa and L929 cell lines. Active fractions were fractionated by molecular exclusion chromatography, HPLC and MPLC. The identification of compounds was performed by NMR and FIA-ESI-IT-MS/MS analysis. Apoptotic mechanism was analyzed by flow cytometry, determining the reduction in the mitochondrial membrane potential (JC-1) and the activity of caspases 3, 8 and 9. Cell viability assays showed that the hexane fraction of the methanol extract of the plant has significant effects against cancer lines RAW 264.7 (IC50=52.08±1.06μg/mL) and HeLa (IC50=46.77±1.09μg/mL), the residual fraction showed a selective effect on cell lines M12.Ak.C3.F6 (IC50=59.90±1.05μg/mL), RAW 264.7 (IC50=58.93±1.26μg/mL) and HeLa (IC50=50.11±1.135μg/mL) compared to the control cell line L929 (IC50=100.00±1.09μg/mL). The chemical characterization of the active fractions allowed the identification of β-sitosterol and stigmasterol in hexane fraction and some phenolic acids, proanthocyanidins and flavonoids in the residual fraction. The methanol extract and hexane fraction reduces mitochondrial membrane potential significantly and activates caspases 3, 8 and 9. Because of the antiproliferative activity observed, our results provide a rational basis for the use of extracts of A. californica in treating various types of cancer in traditional medicine from Mexico. The extracts induce apoptosis via activation of caspases.