Background: Macrosolen parasiticus (L.) Danser belonging to Loranthaceaea (mistletoe family) is a parasitic plant that grows on different host plants such as mango, jack fruit, peepal, neem tree, etc., This study was aimed to investigate the anti-cancer activity of methanolic and aqueous extract of stem of M. parasiticus. Objectives: To investigate the in vitro cytotoxic potential of the methanolic and aqueous extracts from stems of M. parasiticus against MCF-7 breast cancer cells by brine shrimp lethality (BSL) bioassay, MTT assay and sulforhodamine B (SRB) assay. Materials and Methods: The extracts were tested in human breast cancer cell lines in vitro for percentage cytotoxicity, apoptosis by acridine orange/ethidium bromide staining, LD 50 and IC 50 values after treatment with M. parasiticus extracts. Results: In BSL bioassay, aqueous extract showed more significant (P < 0.01) cytotoxicity with LD 50 82.79 ± 2.67 μg/mL as compared to methanolic extract with LD 50 125 ± 3.04 μg/mL. The methanolic extract of M. parasiticus showed IC 50 97.33 ± 3.75 μg/mL (MTT) (P < 0.05) and 94.58 ± 3.84 μg/mL (SRB) (P < 0.01) assays against MCF-7. The aqueous extract of M. parasiticus demonstrated higher activity with IC 50 59.33 ± 3.3 μg/mL (MTT) (P < 0.01) and 51.9 ± 1.87 μg/mL (SRB) (P < 0.01) assays, after 48 h of exposure and thus showed significant dose-dependent cytotoxic activity. Conclusion: The finding demonstrated that both extracts of M. parasiticus showed significant cytotoxic activity, however aqueous extract demonstrated higher activity against MCF-7 breast cancer cells.