Abstract: With the continuous acceleration of global industrialization, the conflict between energy supply and demand has intensified. The excessive consumption of traditional fossil fuels not only triggers resource depletion crises but also causes severe environmental issues. Consequently, the development and utilization of sustainable energy sources have emerged as a globally recognized core pathway to resolving the energy crisis. Among various energy conversion technologies, photocatalysis has emerged as a prominent research hotspot in the energy and materials fields in recent years. This technology offers a highly innovative solution for transforming and upgrading energy structures by directly converting clean, renewable solar energy into stable, high-energy-density chemical fuels—such as hydrogen and hydrocarbon fuels. Cu-based quantum dots (QDs), as a novel class of semiconductor nanomaterials, have gained prominence in photocatalysis owing to their unique advantages, including quantum size effects, tunable light absorption properties, and high charge carrier mobility. Furthermore, compared to traditional precious metal-based catalytic materials, Cu-based QDs benefit from eco-friendliness, abundant raw material reserves, and low cost, making them better aligned with the practical requirements of large-scale applications. Consequently, they demonstrate irreplaceable and broad application prospects in the field of photocatalysis. This review systematically summarizes recent research advances in Cu-based QDs for photocatalytic solar-to-fuel conversion. First, it outlines the fundamental properties of quantum dots, focusing on their defining features such as quantum size effects and surface effects, along with the most widely employed preparation methods including sol-gel, hot-injection, and hydrothermal synthesis. Second, Cu-based QDs are categorized and discussed based on their chemical composition, encompassing Cu QDs, alloy QDs, oxide QDs, sulfide QDs, and selenide QDs. Building upon this foundation, the application mechanisms and advancements of Cu-based QDs in photocatalytic energy conversion fields—including water splitting for H₂ production, photocatalytic H₂O₂ generation, and photocatalytic reduction of CO₂ to produce hydrocarbon fuels—have been summarized. Finally, future trends and prospects for Cu-based QDs in solar fuel conversion are discussed. This review is expected to provide valuable insights into the rational design and performance optimization of Cu-based QDs photocatalysts and offer some theoretical foundation and experimental guidance for expanding their practical applications in sustainable energy transformation systems.