A spokesman for the Japanese Red Cross Society said Tuesday that a male donor tested positive for HIV this month.
Red Cross spokesman Akihiko Nakano says the man had also donated blood earlier this year, and two people had received the blood.
Results for the second person have not come out yet.
Japan had a similar case in 2003 with one transfusion recipient testing positive.
All donated blood is screened, but the tests are not foolproof, especially when the infection is in its early stages.
About 460 to 470 people test positive for HIV in Japan annually.
Take ABC13 with you!
Download our free apps for iPhone, iPad, and Android devices