We present an experimental proof-of-concept study of organic semiconductor nanoparticles (NPs) for visible-light-driven carbon dioxide (CO2) conversion. Donor:acceptor NPs, consisting of the conjugated polymer donor PM6 and small molecule electron acceptors, namely, PC71BM or Y6, decorated with silver as cocatalyst, produce CH4 with reaction rates of (3.6 ± 0.8) and (4.2 ± 1.4) μmol g−1 h−1, respectively. NPs consisting of PCE10 as donor polymer and ITIC as small molecule acceptor and decorated with gold as cocatalyst, exhibit CO production rates of (4.7 ± 1.2) μmol g−1 h−1. Importantly, the synergetic effect of efficient cocatalyst deposition and charge carrier generation within the NPs determines their photocatalytic activity.