Quantum dots (QDs) have been advanced biomedical applications, including drug delivery. They can be inorganic (e.g., ZnO, CdS, CdTe, Si QDs, CuInS₂) and organic-based (e.g., carbon QDs, graphene quantum dots) materials. They exhibited advantages such as high surface area, high photostability, and can be modified merely using different approaches such as in-situ synthesis and postsynthetic method. QDs can be modified with biomolecules such as polysaccharides, proteins, polymers, and DNA leading to the formation of a hybrid QD system. Hybrid systems consist of QDs, and other molecules serve as a carrier for drug delivery of various anticancer drugs. The modification of QDs using these molecules mitigates their cytotoxicity and improves their performance as carriers. This chapter summarizes the applications of hybrid systems based on QDs for drug delivery. It also concludes a short introduction regarding QDs and their cytotoxicity. This study gives valuable insight into the fact that the performance of QDs as a carrier for drug delivery does not solely depend on a single factor but rather depends on a combination of elements from the particle formulations and the extent of cellular uptake.