In this work, our objective is to understand the influences of chemically functionalized carbon nanotubes (covalent) in combination with non-covalently functionalized for enzyme immobilization on a support graphite electrode. We hypothesize that enrichment of surface functionalities of carbon nanostructures allows high-density immobilization of bilirubin oxidase to electrocatalytically reduce oxygen to water along with good stability and large electrocatalytic currents. Although, several reports appear on separate covalent or non-covalent carbon nanotubes functionalization for enzyme immobilization, this study is the first of its kind that aims to obtain quantitative insights on the effect of synergistic combination of covalent plus noncovalent strategies for enzyme immobilization and electrocatalytic applications.