This work describes the preparation of an amperometric sensor for electrocatalytical detection of L-cysteine (Cys). The developed sensor is based on a functional platform to complex copper ions on multi-walled carbon nanotubes (MWCNTs) modified with poly-4-vinylpyridine (PVP) through an in situ polymerization. The obtained values for the kinetic constants of heterogeneous electron transfer rate (k(s)) and for chemical reaction (k(obs)) between Cu2+ and cysteine were 5.78 s(-1) and 6.96 L mol(-1) s(-1), respectively. The analytical curve showed a linear response range for detecting L-cysteine in concentrations from 5 to 60 mu mol L-1. The detection and quantification limits obtained were 1.50 and 5.00 mu mol L-1, respectively with a response time of 0.10 s at an applied potential of 150 mV vs SCE. (C) 2012 Elsevier Ltd. All rights reserved.