Ficus religiosa plant is an important medical plant and traditionally used to treat various diseases including mastitis, otitis media, pharyngolaryngitis, urethritis, dysmenorrhea and diabetis. The present study was conducted to evaluate anti-tumour properties of Ficus religiosa leaves collected from Baghdad, Iraq. 1- Test different extracts of Ficus religiosa plant (chloroform, butyl alcohol, absolute methanol and a crud aqueous extracts) to determine the cytotoxic effect on breast cancer (MCF7), prostate cancer sensitive to docetaxel (PC3) and resistance to docetaxel (PC3-TxR), leukemic cancer cells sensitive to daunorubicin (K562) and resistance to daunurobicin (K562Dox) cancer cell lines using sulforhodamine B assay. Then choose the best extract caused cancer cell inhibition to study chemosensitizing effect on cancer cell lines using sulforhodamine B assay. HPLC-DAD was used to determinate the active compounds in plant extract and study its ability for inhibition P-gp, EGFR, NrF2, Id1, Id2, Id3, Patch1 and Gli2 genes expression on PC3-TxR cells using RT-PCR and Western blot. 2- Investigate the toxic effect of extract in vivo by determination of LD50 and evaluate anti-tumour (histopathologically and immunohistochemically for P-gp gene expression) in SCID mice. The in vitro results of inhibition concentration (IC50) against cell lines demonstrated that treatment of cell cultures with four Ficus religiosa extracts decreased inhibitor concentrate (IC50) of the cells significantly (P≤0.05) and the effect was dose. The chloroform extract with low IC50 caused high toxic against PC3-TxR while a crud aqueous extract had less toxicity against cancer cell lines. The chloroform extract revealed that the extract exhibited strong chemosensitizing effect (CE) on PC3-TxR cell line than other cancer cell lines. Chemical analysis of chloroform extract was carried out using high performance liquid chromatography (HPLC-DAD) analysis. Accordingly, five different compounds (quercitin, myrecitin, tannic acid, gallic acid and serotonin) were characterized. The results displayed tannic acid and serotonin in the extract, while the other pure compounds have not been reported and there were many other compounds in the extract were considered unknown. The highest concentration of tannic acid was observed in the extract while serotonin was less concentration. Moreover, the chloroform extract had potent inhibitory cytotoxic effected against the proliferation of PC3-TxR cancer cells, through down-regulation of P-gp, Id1 and Id2 genes expression and the effect was markedly detect after 24 hours of treatment. The Western blot result confirmed chloroform extract inhibit P-gp protein production in PC3-TxR cancer cell lines. Lethal dose (LD50) of chloroform extract of Ficus religiosa leaves was 11.3 g.Kg-1 and the results showed the chloroform extract was significantly effective in reducing tumour size in a dose-dependent manner, when compared with mice intravenous (i.v) with docetaxel (20 mg.Kg-1) once weekly which associated with adverse side effects as well as observed reduction in mice weights more than 30% compared with negative and positive groups. Histopathological examinations of tumour sections from treated mice revealed decreased of mitosis and increased vascularization of cells. The P-gp gene showed a positive expression in tumour cells treated with docetaxel alone (positive control), while it showed a decreased expression in tumour sections of animals treated orally with the dose 3.8 g.kg-1 and at the dose 7.5 g.kg-1. The results revealed that Ficus religiosa extract has anticancer activity against cancer cell in vivo and in vitro.