Background: The only curative therapy for many primary immunodeficiencies is HSCT. aGvHD is a serious and potentially fatal complication of HSCT with an incidence of nearly %50. Furthermore, involvement of the lower gastrointestinal (LGI) tract is associated with a poor prognosis. Unfortunately, there isn’t consensus about second-line therapies for steroid-refractory (SR) aGvHD. Alpha 1 Antitrypsin (AAT) is one of the second-line therapies. There isn’t a study in pediatric population with acute SR-GvHD in the literature. Method: We retrospectively evaluated data of 3 patients that received AAT as second-line therapy for acute SR-GvHD. Results: Each patients’ response to treatment was unique. P1 had a complete response beginning with the third dose of the treatment. P2 showed a partial response to the treatment after the second dose. Despite 8 doses of the treatment, P3 did not achieve remission. Conclusion: AAT may play a promising role in the treatment of severe and refractory aGvHD in children, without causing an additional immune suppression in opposite to agents which were placed in guidelines. Further studies are warranted with AAT for pediatric population.