Diamond exhibits good biocompatibility and a large electrochemical potential window, and thus, it is partic-ularly suitable for bio-functionalization and bio-sensing. Modification of the diamond surface can be achieved through mussel-inspired surface chemistry based on polydopamine (PDA) while maintaining the intrinsic properties of the surface. We present a comparative study on the polymerization/deposition of PDA from an aqueous solution of dopamine on hydrogen-(H) and oxygen-(O) terminated nanocrystalline diamond films (NCD). The dopamine poly-merization/deposition was performed under mild conditions, which resulted in a confluent PDA layer. A detailed investigation of the growth kinetics of the PDA film on H-and O-terminated NCD substrates was performed using spectroscopic ellipsometry. The chemical composition, the functional group distribution, the surface topography and the wetting properties of the adherent PDA films were evaluated using X-ray photoelectron spectroscopy, atomic force microscopy and water contact angle goniometry, respectively. According to the results, a PDA layer can be used as a platform for future bio-functionalization and/or optical bio-sensing applications.