A glassy carbon electrode (GCE) modified with electropun tricobalt tetroxide nanoparticles decorated carbon nanofibers (Co3O4-CNF) were first applied for the determination of L-tryptophan (L-Trp). The synthesized Co3O4-CNF was characterized by scanning electron microscopy, Raman, X-ray diffraction and electrochemical impedance spectroscopy. The electrochemical detection of L-try was successfully conducted in 0.1 M phosphate solution (pH 2). The linear relationship of L-Trp was in the range of 0.005-40 mu M and the detection limit reached 0.002 mu M (S/N = 3) with little interference from other amino acids. (C) 2016 Published by Elsevier B.V.