Tyrosine kinase inhibitor (TKI) treatment has dramatically improved the outcome of chronic myelogenous leukemia in the chronic phase (CML-CP). However, one study has reported a less favorable treatment outcome with TKIs in adolescents and young adults (AYA) when compared with older patients. In the present study, we retrospectively reviewed the response to TKIs in a Japanese population of 133 CML-CP patients divided into an AYA group (n = 19) and an older group (n = 114). At diagnosis, AYA patients presented with higher white blood cell counts and lower percentage of basophils, and with lower Hasford scores, but no difference was observed in EUTOS score. Probability of achieving complete cytogenetic response was not statistically different between the groups. However, the probabilities of achieving major and complete molecular responses were significantly lower in the AYA group compared to the older group (61 vs 87 % and 17 vs. 33 % at 24 months, respectively; P < 0.05). In addition, a 7-year event-free survival was significantly lower in the AYA compared to the older adults (58 vs. 80 %, P < 0.05). These results suggest that AYA Japanese patients with CML-CP tend to have an unfavorable outcome on treatment with TKI.