The self-assembly and electrochemical properties of a new class of thiol-functionalized azobenzene derivatives were studied on gold electrodes by cyclic voltammetry, The compounds (referred to as CnAzoC2 n = 1-4) were synthesized and characterized in our laboratory. They spontaneously adsorb onto a gold surface to form stable and reproducible monolayers. The CnAzoC2, SAMs (n = 1-3) showed well-behaved voltammetric responses in aqueous solution that corresponded to a two-electron, two-proton reduction/oxidation of the azobenzene redox center. The voltammetric behavior was irreversible, exhibiting very large peak-to-peak splitting and other distortions. The apparent, electron-transfer rate decreased with an increase of carbon atoms in the end group. In contrast to CnAzoC2(n = 1-3), the C4AzoC2 SAM did not show a clear-cut electrochemical response. The disparities between the electrochemical behaviors of these azobenzene SAMs were explained by the structural effect arising from different end groups.