Carbon nanotubes (CNTs) are high aspect ratio allotropes of carbon. Because of their unique physical and chemical characteristics, they are nominated for a vast variety of applications in the biomedical field. Their very low solubility is the only problem of them which is solved by different methods of Functionalization. After discoveries in the last few years of the capacity of CNTs to penetrate into the cells, and because of the low toxicity they display and are not immunogenic, CNT are known to have impressive potentials to be used as drug and medicine carriers and therefore they hold great potential in the field of nanobiotechnology and nanomedicine. CNTs can be functionalized with different therapeutic molecules and internalized by a variety of cell types to deliver therapeutic and diagnostic small molecules and macromolecules to cells. In this review, we will describe the potential of functionalized carbon nanotubes to deliver different types of therapeutic molecules.