Indium-based quantum dots (InQDs), including both III–V (e.g., InP and InAs) and I–III–VI (e.g., CuInS2, CuInSe2, and AgInS2) families, have attracted growing attention as environmentally friendly alternatives to traditional Cd- and Pb-based QDs for photocatalytic energy conversion and environmental applications. Their size- and composition-tunable electronic structures, broad visible-light absorption, and excellent photochemical stability under most circumstances make them ideal platforms for driving various photocatalytic reactions, including hydrogen evolution, carbon dioxide reduction, and organic transformations. This review systematically summarizes recent advances in the rational design and performance optimization of InQDs for photocatalytic applications, with a particular focus on structural modulation, surface passivation, and interface engineering strategies that enhance charge separation and suppress nonradiative recombination. We further elucidate the fundamental relationships between the composition, shell configuration, and defect states of InQDs and their corresponding catalytic activities and stabilities. In addition, emerging strategies, such as co-catalyst coupling, heterostructure construction, and hybrid integration, are discussed to enhance light harvesting and reaction kinetics. Finally, the current challenges and future perspectives are outlined, including scalable green synthesis, precise interfacial control, and data-driven design, which provide insights to accelerate the development of high-efficiency, heavy-metal-free InQDs for sustainable photocatalytic hydrogen generation, CO2 conversion, and organic transformations.