Cancer, one of the leading causes of death, usually commences and progresses as a result of a series of gene mutations and dysregulation of expression. With the development of clustered regularly interspaced palindromic repeat (CRISPR)/Cas9 gene‐editing technology, it is possible to edit and then decode the functions of cancer‐related gene mutations, markedly advance the research of biological mechanisms and treatment of cancer. This review summarizes the mechanism and development of CRISPR/Cas9 gene‐editing technology in recent years and describes its potential application in cancer‐related research, such as the establishment of human tumor disease models, gene therapy and immunotherapy. The challenges and future development directions are highlighted to provide a reference for exploring pathological mechanisms and potential treatment protocols of cancer. [ABSTRACT FROM AUTHOR]