Every year, cancer takes the life of millions of people. Conventional treatments have produced unsatisfactory results for some types of cancer, and the side effects are extensive, leading to a shift in the focus of treatment towards alternative medicines. Indeed, medicinal plants have long been investigated by scientists for their anti-cancer properties. Some phytochemicals that are important active constituents of plants, including catechins, ursolic acid, silymarin, glycyrrhizin, ellagic acid, gallic acid and various types of flavonoids, have shown promise in future cancer management. The current review covers various aspects of cancer treatment based on medicinal plants at molecular level and sheds light on their structures and modes of action.