Carbon nanostructures, carbon nanotubes (CNTs) and reduced graphene oxide (rGO) have been used to modify the electrodes to decrease the over potential and improve the sensitivity. In this tutorial article, we focus on recent literature that describes how CNTs-and rGO-modified electrodes are being used for electrochemical investigations of several biologically important molecules or pharmaceutical drugs. Huge electroactive surface area and superior electron transfer properties make CNTs and rGO good candidates for electrode materials. Various electrochemical techniques viz., cyclic voltammetric, differential pulse voltammetric, stripping voltammetric, amperometric etc., have been used to explore detailed electrochemistry of biomolecules and to develop electroanalytical methods for their assay in pharmaceutical formulations and biological samples. Future challenges lie in the development of selective, sensitive, reproducible and simultaneous determination of biomolecules.