Although allogeneic hematopoietic stem cell transplantation (HSCT) is an established treatment for Philadelphia chromosome-positive acute lymphoblastic leukemia (ALL), the prognosis of patients who relapse after allogeneic HSCT has been extremely poor. Dasatinib, a second-generation tyrosine kinase inhibitor, is a promising agent for the treatment of Ph-ALL. We report on a Ph-ALL patient who relapsed early after the first allogeneic HSCT, but achieved complete molecular remission with dasatinib alone. She remains in molecular remission 12 months after the second allogeneic HSCT. Dasatinib was generally well tolerated, but she developed myalgia, nausea and positive cytomegalovirus antigenemia. In addition, sudden-onset bloody diarrhea was observed 10 days after the second HSCT, which was possibly associated with the use of dasatinib in addition to the effect of the conditioning regimen and graft-versus-host disease. In conclusion, dasatinib is an effective agent for Ph-ALL with a poor prognosis, but may be associated with specific adverse events including opportunistic infection and gastrointestinal bleeding.