Carbon nanotubes (CNTs) have been proposed and are actively being explored as innovative multipurpose carriers for biomolecules and diagnostic applications. Their versatile physico-chemical features enable them as a carrier of several pharmaceutically relevant entities and allow them for rational design of novel nanoscale candidates for drug development. Functionalized carbon nanotubes (f-CNT) are emerging as a new family of nanovectors for the delivery of different types of therapeutic molecules. The application of CNTs in the field of carrier-mediated delivery has become possible after the recent discovery of their capacity to penetrate into the cells. CNT can be loaded with active molecules by forming stable covalent bonds or supramolecular assemblies based on noncovalent interactions. Once the cargos are carried into various cells, tissues and organs they are able to express their biological function. In this review, we will describe the potential of f-CNT as a vehicle to deliver different types of therapeutic agents into the biological species.