This work presents a method for the preparation of isocyanate functionalized graphene-regioregular poly 3-hexyl tiophene (rr-P3HT) nanocomposites. Graphite oxide prepared by the Hummer's method and half blocked tetramethyl xylylene isocyanate (Et-TMXDI) are the precursors for the new obtained isocyanate functionalized graphene. Fourier transform infrared spectroscopy, UV-vis spectroscopy, Xray diffraction, atomic force microscopy, Scaning electron microscopy and Raman spectroscopy were used to characterize the functionalized graphene. The isocyanate functionalized graphene facilitates selfassembling of P3HT polymer in highly oriented nanowires. Thin films of functionalized graphene -rrP3HT nanocomposites obtained by spinning and dip coating processes were investigated and used for organic field effect transistors (OFETs). The doping of P3HT with the new functionalized graphene increases the mobility and also the photoresponse of OFETs in deep UV and UV range. (C) 2013 Elsevier B.V. All rights reserved.