Microelectrodes have received tremendous attention in different fields due to their unique electrochemical properties caused by small size. Here, we report a facile method for fabricating a hemoglobin-graphene modified carbon fiber microelectrode (Hb/GCFME) as a H2O2 electrochemical microsensor. Three-dimensional porous graphene layer was deposited electrochemically on the surface of carbon fiber, and then hemoglobin was introduced by a simple dipping method. The immobilized hemoglobin retains its bioactivity and the direct electrochemistry of hemoglobin at Hb/GCFME exhibits a couple of well-defined redox peaks with a formal potential of -0.36 V. Moreover, Hb/GCFME shows a good electro-catalytic activity towards H2O2 and can be used for sensitive detection of H2O2. By amperometry, the microbiosensor exhibits a wider linearity range from 8.0 mu M to 0.21 mM with a detection limit of 2.0 mu M and much higher sensitivity of 1.4 mA cm(-2) mM(-1). This microsensor has potential application in the detection of H2O2 in microsystems, and the method developed in this paper offers a new way for fabricating redox protein/enzyme-based microsensors. (C) 2015 Elsevier Ltd. All rights reserved.