We report a case of spontaneous pregnancy with subsequent full-term live birth following hematopoietic stem cell transplantation (HSCT) for mycosis fungoides in a 24-year-old nulligravida with 4 years of prior infertility due to primary ovarian insufficiency. Four months post-transplant, the patient was found to be 10 weeks pregnant. Her pregnancy was complicated by first trimester fetal exposure to mycophenolate mofetil (pregnancy category D), delayed-onset acute gastrointestinal graft-versus-host disease, and multiple systemic infections. This report highlights the importance of discussing potential fertility outcomes in patients undergoing HSCT, including the necessity for adequate contraception post-transplant, even in the setting of previous infertility.