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A bifunctional sensor for determination of reduced β-nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H2O2) has been successfully fabricated by xanthurenic acid (Xa), flavin adenine dinucleotide (FAD), and functionalized carbon nanotubes (CNTs). The hybrid composites can be easily prepared by the electrocodeposition of polyXa/FAD and the adsorption of functionalized CNTs. These composites can be constructed of “polyXa/FAD/CNTs” and “CNTs/polyXa/FAD” according to the immobilization order of polyXa/FAD “before” and “after” the adsorption of CNTs. They are surface-confined and stable in various scan rates and different pH conditions. Particularly, the polyXa/FAD/MWCNTs show more efficient activity to target species due to the compact structure and more active surface area. It provides linear concentration range of 5×10−6–1.7×10−4 M and 1×10−4–2.9×10−3 M, with sensitivity of 155μAmM−1 cm−2 and 60μAmM−1 cm−2, and detection limit of 10−6 M and 10−4 M (S/N=3) for NADH and H2O2, respectively. No interference except of the case for NADH determination in the presence of AA. It can be a good electrocatalyst to determine NADH and H2O2 and the linear sweep voltammetry (LSV) technique can help to analyze NADH from the AA interference. [ABSTRACT FROM AUTHOR]