Donor–acceptor (D–A) polymers are promising materials for organic electronics because of high charge carrier mobilities and narrow band gaps. Despite recent progress, there is incomplete understanding of the mechanisms underlying charge transport in these materials. In this work, we use single molecule techniques to study intrachain charge transport in D–A oligomers containing alternating diketopyrrolopyrrole (DPP) acceptor and bithiophene donor units. Interestingly, at high applied bias, longer DPPTT oligomers exhibit substantially higher conductance compared to shorter oligomers, which is interpreted using density functional theory (DFT) simulations. Overall, this work provides an increased understanding of intrachain charge transport along D–A oligomers.