Controlling defects is one of the basic strategies for tailoring electronic structure of materials, which has not been explored that much yet for organic-inorganic hybrid systems. In this study, we investigated the control of work function of oxide electrode by defect-associated adsorption of molecules at the single-molecule level by means of scanning tunneling microscopy and first principle calculations. The equilibrium adsorption configuration of monoethanolamine (MEA, HO(CH2)(2)NH2), an effective coating for lowering the work function of an oxide electrode, varies as a function of surface coverage at TiO2(1 1 0) surfaces. Our results showed that defects at the oxide surface and intermolecular interactions dominate the stable configuration of adsorbates as well as work function of the system. The dissociative adsorption at O-v was found to be more efficient at lowering the work function of TiO2(1 1 0) surface, suggesting that defect control can be used to improve the performance of organic-inorganic hybrid systems.