The Jr(a+) antigen is one of the high-frequency antigens belonging to the JR blood group system. Although the clinical significance of anti-Jra is not well defined, cases of hemolytic disease of the newborn and hemolytic transfusion reactions caused by anti-Jra have been reported. This review introduces the genetic background of the JR blood group, the frequency of Jr(a+), and the clinical significance of anti-Jra based on existing literature. Additionally, it summarizes the identification of anti-Jra and the transfusion strategies that can be adopted for patients with anti-Jra alloantibodies.