In this study we demonstrate that the ambipolar behaviour, and particularly the hole transport, of an n-type polymer semiconductor poly [N, N 9-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)], P(NDI2OD-T2) can be enhanced by co-deposition with liquid phase exfoliated graphene. The field-effect mobility of holes can be increased by 45 folds for 2.5 µm channel length devices at the blend ratio 150:1, i.e. 0.6%, in weight while keeping the Ion/Ioff ratio as high as 103 and shifting the threshold voltage closer to zero. The improvement is due to a better energy level alignment of the graphene with the work function of the electrodes, and to the creation of percolating pathways for the transport of charges as a result of the embedment of the graphene sheets in the n-type polymer matrix. Our strategy of combining the high performance of graphene and the ideal film forming ability of conjugated polymers in a simple one-step deposition process provides a prospective pathway for the application of graphene based nanocomposites for logic circuits