The present work reports a facile approach to the one-pot solution growth of vertically aligned, doped ZnO nanorod (NR) arrays by chemical bath deposition (CBD). The effects of dopant ions on the final morphologies, electronic band structures and donor densities of ZnO were examined. With the introduction of dopants, the optical band gap energies of the samples were reduced. The photoelectrochemical (PEC) water splitting performances of the doped ZnO NRs were tested. When compared with pristine ZnO NRs, the doped ZnO NRs demonstrated an improvement of at least 15% in the PEC water splitting activity. Na-doped ZnO NRs was the most efficient anode, where its photocurrent density was 2.1 times greater than that of pristine ZnO NRs. The mechanism for improved PEC performance was proposed.