Conductance switching associated with the photoisomerization of azobenzene-based (Azo) molecules was observed in nanoscopic metal-molecule-metal junctions. The junctions were formed by using a conducting atomic force microscope (C-AFM) approach. where a metallic AFM tip was used to electrically contact ago-supported Azo self-assembled monolayer. The measured 30-fold increase in conductance is consistent with the expected decrease in tunneling barrier length resulting from the conformational change of the Azo molecule.