Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment for children with life-threatening hematological diseases, but the procedure comprises a high risk of infertility. We have previously shown that two-thirds of male survivors had azoospermia median 18 years after pediatric HSCT [1]. However, some patients with azoospermia may produce sperm that do not reach the ejaculate, giving hope for biological paternity. Microdissection testicular sperm extraction (mTESE) is a surgical procedure for men with non-obstructive azoospermia [2]. During mTESE, the testicular tissue is systematically examined using an operating microscope to identify dilated seminiferous tubules that may contain active sperm production. Biopsies from such areas are examined for the presence of mature spermatozoa that, if found, are cryopreserved for assisted reproduction. mTESE is not routinely offered to men with azoospermia after HSCT, and the literature is, to our knowledge, limited to 15 case reports worldwide [3,4,5]. Here we present a case series of five male survivors of pediatric allogeneic HSCT who, due to their wish of biological paternity, underwent mTESE for the purpose of future assisted reproduction.