Cancer is not left with the space untouched, however, a complete cure has not been achieved. Researchers are working extensively to bring a new edge to the treatment regimen. Unfortunately, due to dynamic genetic changes of cancerous cells and the necessity to eventually conquer malignant cell or tumor resistance, these innovations are frequently just temporary. This creates a never-ending need for overcoming resistance and improving survival. It is worth mentioning that Quantum Dots (QDs) in the field of nanotechnology has gained enormous attention in cancer diagnosis and its treatment. Owing to extensive biocompatibility, adjustable surface functions, and high-water solubility, quantum dots have become nanoparticle of interest in medical applications. The present review focuses on the various applications of quantum in the diagnosis of cancer, including early detection of primary as well as the drug delivery mediated by quantum dots. As a means of improving their functionality, we highlight various QD kinds and characterization techniques in this review. We have also concentrated on using QDs as a drug delivery system, diagnostic tool, drug delivery system, or tool to research biological processes. We conclude by talking about QDs' current limits and upcoming difficulties.