Poly(2-hydroxyethyl methacrylate) brushes were grown from a gold substrate by Atom Transfer Radical Polymerization (ATRP) and the material was applied as the gate dielectric layer in Organic Thin Film Transistor (OTFT) devices. The ATRP method provided 120 nm thick layers with relatively low roughness, as characterized by Atomic Force Microscopy. The layers were also investigated by Fourier Transform Infrared Spectroscopy to confirm that the polymer layer was covalently bonded to the gold surface. The synthesized polymer had very low dispersity, D = 1.18, indicating the well-controlled polymerization process. Dielectric Spectroscopy was used to characterize dielectric properties of the layers for potential use as the gate dielectric in OTFTs. Then, an OTFT device was subsequently constructed by deposition of a pentacene derivative as the semiconductor on the dielectric layer. The OTFT exhibits a field-effect for a relatively low operational voltage range (V-DS < 30 V and V-GS < 15 V). This study demonstrates that the ultrathin layers of polymer brushes grown by ATRP can be integrated into organic electronic devices such as OTFTs.