Ganoderma is a medicinal mushroom that has been used for years for treatment of various diseases. Ganoderma mushroom was considered as "mushroom of immortality" in traditional Chinese medicine and was used to cure many diseases including cancer. Over the last 50 years, phytochemical studies led to isolation of more than 500 secondary metabolites from various Ganoderma species including lanostanes, triterpenes, meroterpenoids, sesquiterpenoids, hydroquinones, steroids, alkaloids and polysaccharides.  In vitro and in vivo studies showed that Ganoderma mushrooms possess a wide range of biological activities, including anticancer, antihyperlipidemic, hypoglycemic, anti-inflammatory, antioxidant, antiplatelet aggregation, antiplasmodial, and antiviral activity. This review summarizes bioactive compounds isolated from different species of Ganoderma. The isolated compounds were tested for their anti-tumor in vitro activities in MCF-7 and MDA-MB-231 breast cancer cell lines. Ergosterol peroxide showed selective inhibition of MCF-7 (ER +ve) cell lines relative to MDA-MB-231 (ER -ve) cell lines with an IC₅₀ of 12.9 µM and 91 µM respectively.