Graphene has a superior potential as a preferable platform in sensing and catalysis application. Here, we proposed amino-graphene as a straightforward platform for immobilization of biomolecules toward sensing of cancer diagnostic. MicroRNA-155 is selected, since it is known to play an important role in many cancer diagnostics. The process of sensor fabrication is simple and includes of two steps: (1) preparation of amino-graphene and assembling of it on the surface of electrode, (2) attaching of antimicroRNA- 155 into amino-graphene through crosslinking by glutaraldehyde. Different steps of biosensor fabrication are characterized by atomic force microscopy and electrochemical impedance spectroscopy, and hybridization of target microRNA-155 with its complementary is assayed by differential pulse voltammetry. Hence, biosensor is able to detect the miRNA-155 at femtomolar concentration level and the proposed platform can be simply applicable for immobilization of different biomolecules for numerous applications.