Cysteamine adsorbs spontaneously onto gold surfaces forming a uniform and active amino-group-terminated monolayer. The electroactive azobenzene group was anchored to the monolayer through an amide surface reaction. Thus-formed azobenzene self-assembled monolayers were further subjected to exchange in dilute pentanethiol solution. At each step of modification, the surface was characterized by both contact-angle titration and cyclic voltammetry. Contact-angle titration data acquired for the pure cysteamine monolayer exhibit a smooth transition in contact angle between plateau regions at low and high pH. It was found that the titration curves shift significantly in the higher contact-angle direction, i.e. increasing surface hydrophobicity, after azobenzene was immobilized and was further exchanged with pentanethiol. The cyclic voltammograms showed reversible surface waves for the immobilized azobenzene groups, and showed further changes due to packing of the monolayer. The results demonstrate the possibility of structure-controlled functional molecular assembly by using step-by-step surface modification and that the combined application of contact-angle titration and electrochemistry is useful in monitoring surface reactions.