In the early 2010s, scientists realized that CRISPR/Cas9, a bacterial immune defense system against viruses that involves the CRISPR-associated protein #9 (Cas9) endonuclease enzyme, single-guide RNAs (sgRNAs), and PAM recognition, could be used to intentionally manipulate genes, essentially changing gene expression and regulation in such a way that would allow for a customized genome. Since then, CRISPR technology has revolutionized medical research and the biotechnology industry, and its newfound capabilities have scientists asking if CRISPR can be used to modify genes in such a way that would cure or treat certain harmful or life-threatening diseases. There have been CRISPR-based clinical studies done to treat β-thalassemia (TDT), sickle-cell disease (SCD), the human immunodeficiency virus (HIV), and several other genetic and non-hereditary diseases, but there is still a long way to go before CRISPR can become a widespread treatment for many more such diseases (Ebina et al., 2013; Esrick et al., 2021; Frangoul et al., 2021). Currently, researchers are looking to see if CRISPR is an accurate, specific, non-harmful, and effective treatment for these diseases, which means addressing and eliminating potential concerns about its safety and efficacy through extensive pre-clinical and clinical research, as well as overcoming moral and social obstacles. In this review, I will look at how the CRISPR/Cas9 gene-editing system can be applied in humans to prevent, cure, or treat these diseases, as well as what needs to be done before the CRISPR/Cas9 system can be made publicly available as a medical treatment for diseases.