This paper is devoted to investigate the effect of carbon nanotubes (CNTs) on charge injection efficiency of organic field effect transistors (OFETs) based on the conjugated donor-acceptor copolymer; poly[4-(4,4-dihexadecyl- 4H-cyclopenta[1,2-b:5,4-b′]-dithiophen-2-yl)-alt- [1,2,5]thiadiazolo-[3,4-c]pyridine] (PCDTPT). Charge injection in organic devices might be limited by Schottky barriers between metal electrodes and organic semiconductors. This effect leads to deterioration of the overall transistor performance. CNTs are appropriate materials to be used as source and drain electrode of OFETs. The one-dimensional (1D) structure of CNTs induces strong electrostatic effects at the electrode/semiconductor interface, which promotes charge carrier tunneling across the contact Schottky barriers. In this work, CNTs were deposited by vacuum filtration method on membrane following by transfer from membrane on silicon wafer substrate. Three different electrodes, i.e. Gold (Au), Titanium (Ti), and CNT were compared for OFETs with bottom gate-bottom contact configuration. CNTs electrodes showed better injection performance compared to Au and Ti electrodes. Also, the value of the field effect mobility of the devices increased by one order of magnitude for device with CNT electrode compared to Au electrode. Keywords: Carbon nanotubes (CNTs), Organic field effect transistor (OFET), Charge injection efficiency, poly[4-(4,4-dihexadecyl- 4H-cyclopenta[1,2-b:5,4-b′]-dithiophen-2-yl)-alt- [1,2,5]thiadiazolo-[3,4-c]pyridine] (PCDTPT), Schottky barrier.