Polyoxometalates are a class of well-defined metal oxygen clusters mostly known for their catalytic properties. However, their electronic and optical properties have been used in device applications such as electrochromic displays, dopants for conductive polymers, gas and chemical sensors, capacitors, and electrochemical cells. We fabricate nanodevices based on a composite poly(methyl methacrylate) H3SiW12O40 system and we investigate the effects of electrode material, electrode distance, and molecular concentration on the electronic transport characteristics. It is found that in the case of electrode distances smaller than 50 nm, tunneling effects appear, which are discussed using tunneling theory models. These effects are primarily dependent on the electrode distance and molecular concentration, and less on the electrode material.