Changes in the optical properties of single gold nanorods during electrocatalytic oxidation of glucose in alkaline media are monitored in real-time by single-nanoparticle dark-field spectroelectrochemistry. The spectral scattering characteristics under dynamic potential scan conditions are closely related to the electrochemical processes, and the electrochemical catalytic mechanism of the process is discussed. Moreover, changes in free-electron density are evaluated using a Drude dielectric function with charge density-modification. The proposed sensing technique based on plasmonic analysis shows significant promise for the design and research of electrochemical catalytic systems at the single-nanoparticle level. (C) 2016 Elsevier B.V. All rights reserved.