<p>Uranyl ions (UO₂²⁺) present serious environmental and health risks due to their long half-life and bioaccumulation. Fluorescent sensors, particularly carbon dots (CDs) nanocomposites, offer a promising solution with high sensitivity, low toxicity, rapid response, and cost-effectiveness. This review summarizes advances in the synthesis of CDs and their nanocomposites for uranyl ion detection including hydrothermal, microwave-assisted, electrochemical, pre-assembly, in-situ recombination, and one-pot approaches and discusses their impact on CDs’ properties. We focus on detection mechanisms such as photoinduced electron transfer, inner filter effect, aggregation-induced quenching, and energy transfer, which enable detection limits as low as nanomolar levels. The current challenges, such as poor selectivity against interfering ions and difficulties in applicability to complex real-world samples, are discussed, along with prospects for smartphone-based portable sensor integration and multimodal detection platforms.</p>