Quantum dots (QDs) are semiconductor nanocrystals with diameters ranging from 2 to 10 nanometers. The development of QDs has greatly advanced nanotechnology, and this achievement was recognized with the awarding of the 2023 Nobel Prize in Chemistry. They have gained significant attention in the field of biomedical applications due to their high adjustability, stability, sensitivity, and selectivity. QDs have proven to be suitable for in vivo bioimaging and tracking, medical diagnostics, and drug delivery systems. Their exceptional attributes, like high brightness, resistance to photobleaching, and multiplexing capability, combined with a high surface-to-volume ratio, make them ideal for these applications. Their unique optical and electronic properties can be precisely controlled by adjusting the size and material composition. By modifying their surface or encapsulating them, QDs can be conjugated with specific biomolecules, enabling the visualization and quantitative analysis of target entities. The ability to externally manipulate QDs through magnetic fields, electric fields, acoustic waves, or temperature changes enhances their utility in targeted drug delivery and therapy. In the context of cancer, a leading cause of global mortality with increasing incidence rates, QDs offer innovative approaches to diagnosis, treatment, and prevention strategies. This review summarizes the cutting-edge applications of QDs in cancer, providing insights into the mechanisms and strategies used. It also critically evaluates the advantages and limitations of QDs, including their toxicity profile. The discussion concludes with a perspective on the technical advancements needed to enhance the clinical applicability of QDs and identifies upcoming challenges in their journey towards widespread biomedical use.