Using the density functional theory, the possible non-covalent interactions and six mechanisms of covalent functionalization of the drug penicillamine with functionalized carbon nanotubes (CNT) were investigated. Quantum molecular descriptors of the non-covalent configurations were studied. It was determined that binding of the drug penicillamine with functionalized CNT is thermodynamically viable. COOH functionalized CNT (NTCOOH) has more binding energy than COCl functionalized CNT (NTCOCl) and could act as a favorable system for penicillamine drug delivery within biological and chemical systems (non-covalent). NTCOOH and NTCOCl can bond to the NH 2 , OH and SH groups of penicillamine through OH (COOH mechanism) and Cl (COCl mechanism) groups, respectively. The activation energies, activation enthalpies and activation Gibbs energies of six pathways were calculated and compared with each other. The activation parameters related to the COOH mechanism are higher than those related to the COCl mechanism and therefore, the COCl mechanism is suitable for covalent functionalization. These results could be generalized to other similar drugs.