Résumé : Introduction Peganum harmala L. (P. harmala) is broadly used in folk medicine for the treatment of various diseases including cancer. The seeds in particularly are employed for therapeutic purposes. The present paper investigates the cytotoxic effects of raw alkaloid extracts from different parts of P. harmala including fruits (TAFr), seeds (TASe), roots (TAR) and aerial parts (TAAp); in order to assess traditional claims about the therapeutic potential of this plant. Methods The cytotoxic effects were evaluated on six malignant cancer cells (A549, U373, Hs683, MCF7, B16F10 and SKMEL-28; A549, U373, MCF7 and SKMEL-28 which are resistant to proapoptotic stimuli) by MTT assay and quantitative videomicroscopy analysis. The main alkaloids were quantified by HPLC in the different parts of plant. Results Total alkaloids of the different parts were cytotoxic towards practically all cancer cell lines with IC50 ranging 1–52 μg/mL after 72 h of treatment. Videomicroscopy analysis indicated that the TAFr, TASe and TAR alkaloids affect A549 lung carcinoma cells behaviour and induce a cytostatic effect whereas TAAp extract was cytotoxic rather than cytostatic. TAAp, TAFr, TASe and TAR treatment induced global growth ratio indexes (GGR) of 0.19, 0.26, 0.3 and 0.62, respectively, after 72 h of treatment. Depending on the organe, harmine, harmaline, harmol and vasicine these range between 2 and 90% w/w of the total alkaloids. Conclusion These data indicate that P. harmala alkaloids extract may support the traditional claims regarding its anticancer uses which could be helpful in providing of new cytotoxic agents against chemo-resistant cancer cells.