Hydrogen and other renewable resources derived by sunlight have attracted great attention to sustainable development. But the photochemical performance of diverse systems is restricted because of the poor efficiency of photon absorption, easy recombination of photogenerated electron–hole pairs, and slow transfer of charge carriers. Single-atom catalysts (SACs), in which isolated atoms are supported on the supports without forming nanoparticles, have received increasing interests in photocatalysis due to the high catalytic activity, selectivity, stability, and 100% atom utilization. In this review, we highlight and introduce recent advances in the preparation method of SACs and concrete examples of single-atom photocatalysts used for the hydrogen evolution from water, overall water splitting, CO2 and N2 reduction reaction. At last, we discuss the underlying mechanisms for photocatalytic performance of single-atom catalysts and the prospects for the development of SACs.