Aldehyde dehydrogenase family 1 member A3 (ALDH1A3) is an important member of the aldehyde dehydrogenase family, and is involved in the physiological process of human cells mainly through the oxidation of all-trans retinal to retinoic acid. ALDH1A3 has the potential to be a target for cancer diagnosis and treatment, as a large body of evidence shows that ALDH1A3 participates in regulating the biological characteristics of tumor cells. Recent studies have found that ALDH1A3 also plays a role in promoting the proliferation of smooth muscle cells, which may be closely related to the development of atherosclerosis. In this review, the role and mechanism of ALDH1A3 in modulating tumor biological characteristics and vascular smooth muscle cell proliferation will be summarized.