Propolis is a resinous natural product produced by honey bees by mixing collected buds and exudates of plants with bee wax. Bees use propolis to protect themselves against wind and rain by using it to construct and repair hives. Propolis has a wide range of biological effects as it is a mixture of natural substances, and it is widely used for its anti-inflammatory, anti-oxidant, immunomodulatory, and anti-cancer effects. Propolis has been used in traditional medicine since time immemorial. Research studies on the anti-tumor effects of propolis extracts and components such as flavonoids, phenolic acids, and their esters demonstrate their potential to be used in the development of new anti-tumor agents. Propolis shows an anti-carcinogenic effect against cancers of the brain, head and neck, skin, breast, liver, pancreas, kidney, bladder, prostate, colon, and blood. In-vivo and in-vitro studies have shown that propolis has cytotoxic, anti-genotoxic or anti-mutagenic, anti-proliferative, anti-angiogenic, anti-metastatic, and proapoptotic properties. Its main mechanisms in cancer treatment can be explained as prevention of metastasis, arrest of the cell cycle, induction of apoptosis and alleviation of harmful side effects caused by chemotherapy. The beneficial effects of natural products on human health have been reported in studies to prevent tumor formation and/or suppress the growth of tumors into cancer. In this review, detailed information about the properties, biological effects, and anti-cancer effects of propolis was given by reviewing current literatures.