Background: Breast cancer is the most common cancer found in women. White fungus (Tremella fuciformis) is a candidate for the therapeutic agent because it contains various phytochemical components that potentially become antioxidants and cytotoxic agents against cancer cells. Aim: To determine the phytochemical components, antioxidant activity, and cytotoxic activity of Tremella fuciformis against MCF-7 breast cancer cells. Methods: Maceration and extraction of Tremella fuciformis were done using polar, semipolar, and nonpolar solvents (ethanol, ethyl acetate, and n-hexane). The phytochemical components were analyzed through phytochemical tests, determination of total phenolic and flavonoid contents, and thin-layer chromatography (TLC). The evaluation of antioxidant activity was carried out using DPPH while the evaluation of cytotoxic activity against MCF-7 cells was carried out using the MTT method. Result: The ethanol and ethyl acetate extracts of Tremella fuciformis contained flavonoids and triterpenoids, while the n-hexane extract contained glycosides and triterpenoids. The TLC test showed that there were five compounds in the ethyl acetate and n-hexane extracts, and three compounds in the ethanol extract. Highly active antioxidant activity was shown in the ethyl acetate extract (IC50 = 44.64µg/mL) and weak activity was shown in the ethanol extract (IC50 = 367.87 µg/mL). The ethyl acetate and n-hexane extract had moderate cytotoxic effects on MCF-7 cells (IC50 = 39.04 µg/mL and 43.2 µg/mL, respectively). In addition, the ethanol extract had a weak cytotoxic effect (IC50 = 154.87 µg/mL). Conclusion: Tremella fuciformis has the potential to be developed as a novel therapeutic agent in the management of breast cancer. © RJPT All right reserved.