Immunosuppressive therapy (IST) with antithymocyte globulin (ATG) and cyclosporine A is the standard treatment for aplastic anemia (AA). The ATG formulation in Japan was changed from horse ATG [Lymphoglobulin(®) (LG)] to rabbit ATG [Thymoglobulin(®) (TG)] in 2009. Since then, 12 patients with AA have been treated with TG. Here, we summarize the effectiveness and safety of TG in comparison with data from 14 AA patients treated with LG before April 2009. One subject treated with LG but none treated with TG terminated the treatment due to a grade III adverse effect. The overall 6-month response rate after IST was similar for LG and TG (67 and 75 %). Infection was noted in five (38 %) and four (33 %) subjects treated with LG and TG, respectively. The initial response rate was significantly higher in the early-treatment group treated within a year of diagnosis than in the late-treatment group, who were treated more than a year after diagnosis (85 vs. 29 %, respectively), as reported previously, without apparent differences between the LG and TG groups. We conclude that TG at a dose of 2.5 mg/kg/day for 5 days is effective and safe in Japanese patients with AA.