Aerva javanica (Burm.f.) Juss. ex Schult. (Amaranthaceae family) has many pharmaceutical properties. This study aimed to determine the anticancerous effect of A. javanica methanol extract (AJME) on breast cancer cell lines and prostate cancer cell lines. The antibacterial potency of A. javanica solvent extracts was tested against Micrococcus luteus, Staphylococcus aureus, Pseudomonas aeruginosa, and Shigella flexneri. A screening of five concentrations of A. javanica was done on prostate and breast cancer cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. The results showed that AJME had various levels of cytotoxicity toward both cancer cell lines. A significant decrease in the rate of cancer cells was associated with a higher concentration of the plant extract. The half maximal inhibitory concentration IC50 value was 4.50 µg/ml for the breast cancer cells and 14.51 µg/ml for the prostate cancer cells. The dried and fresh solvent extracts made with methanol and chloroform demonstrated maximum potency against all the tested pathogenic microbes. The petroleum ether and acetone extracts showed moderate activity, while the diethyl ether and hot water extracts had the lowest antibacterial activity. The gas chromatography-mass spectroscopy analysis showed that AJME had various chemical compounds that have many biological benefits. In conclusion, A. javanica is a promising candidate as a natural herb to treat cancers, more so in breast cancer than in prostate cancer, and it has potential as an antimicrobial agent against multidrug-resistant microbes.