Carbon nanomaterials play a vital role in biosensing applications in a wide variety of analytical devices due to their attractive electrochemical properties including relatively high electrical conductivity, wide electrochemical stability, biocompatibility, and chemical inertness. Biorecognition in electrochemical biosensing requires fine-tuning of the electrolyte/carbon interface resulting in the specific binding of the analyte and the measurement of the transduced signal. Successful protein immobilization on carbon nanomaterials can be achieved through surface functionalization methodologies that modify carbon from a naturally inert material to a physico-chemically active interface that can readily react with the analytes of interest. Any surface functionalization method influences electronical properties at the interface of the modified carbon thus interfacial signal transduction strongly depends on the type of surface modification. In this paper, we review the latest strategies for surface functionalization of carbon nanomaterials applied for covalent immobilization of different biomolecular entities. Furthermore, we summarize recently published techniques for carbon functionalization for achieving highly sensitive protein recognition. Some of these methodologies involve "multi-functionalization" of the carbon platforms enabling multiple biomarkers detection. Such advances in functionalization strategies open new windows of opportunity to the future of carbon as a biosensing material of choice. (C) 2018 The Electrochemical Society.