A 26-year-old patient with a history of chemotherapy for acute lymphoblastic leukemia presented with secondary amenorrhea and cyclic abdominal pain, and she was found to have vaginal stenosis due to adhesion of vaginal wall. The cause of the adhesion was considered to be vaginal inflammation induced by anticancer agents themselves. It was also considered that poor estrogenization of vaginal mucosa as a result of gonadotropin-releasing hormone agonist therapy, conducted for ovarian protection during chemotherapy, might have exacerbated it. Because it is more likely than ever for us to encounter patients who will undertake or had undertaken chemotherapy with gonadotropin-releasing hormone agonist therapy, keen observation and proper intervention would be important.