A novel amperometric hydrogen peroxide microcavity electrode (MCE) was fabricated based on sulthydryl-containing multiwalled carbon nanotubes/silver nanoparticle (MWNTs-SH/AgNPs) nanohybrids. Due to the synergistic amplification property of the MWNTs-SH/AgNPs, The modified MCE (MWNTs-SH/AgNPs/MCE) shows a dramatic electrocatalytic effect on the reduction of hydrogen peroxide. The results showed that MWNTs-SH/AgNPs/MCE exhibited linear dependence on H2O2 concentration in the range between 1.0 x 10(-5) and 1.1 x 10(-3) mol/L with a correlation coefficient of -0.9996. The detection limit (signal-to-noise ratio S/N = 3) was 1.7 x 10(-6) mol/L. The response in the current to coexisting interferences on the MCE surface is almost negligible. This novel microsensor has high potential in detection of hydrogen peroxide in biological environments. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.060212jes] All rights reserved.