Glanzmannʼs thrombasthenia is a rare inherited autosomal recessive bleeding disorder caused by platelet dysfunction. Adolescent girls with Glanzmannʼs thrombasthenia may experience problematic heavy menstrual bleeding beginning at menarche; this can be difficult to manage. Here, we report the case of an 11-year-old girl with Glanzmannʼs thrombasthenia who presented with heavy menstrual bleeding at menarche, which was difficult to control. The vaginal bleeding persisted and did not respond to a treatment with packed red blood cells (16 U total), platelet concentrates (70 U total), or administration (>50 doses) of recombinant activated factor VII (rFVIIa). Eventually, a combination of rFVIIa and hormonal therapy (a combined oral contraceptive pill) was introduced. The bleeding stopped at nearly 1 month from onset of menarche. Thereafter, the condition was managed by monthly subcutaneous administration of a GnRH agonist. Management of severe menorrhagia in adolescent patients with Glanzmannʼs thrombasthenia requires close collaboration with gynecologists or adolescent medicine specialists. More clinical studies are required to identify an effective combination of rFVIIa and hormonal therapy for this condition.