Toxoplasmosis is an infrequent infection with a high mortality rate in hematopoietic stem cell transplant recipients, and is usually caused by reactivation of prior, latent infection upon intensive immunosuppression. We report a case of fatal disseminated toxoplasmosis, diagnosed at autopsy, in a 7-year-old boy who received a cord blood graft for recurrent acute lymphoblastic leukemia. This case represents both the first reported case of toxoplasmosis in an engrafted cord blood recipient, and also of graft failure due to toxoplasmosis. Recommendations for toxoplasmosis diagnosis, treatment, and prophylaxis in stem cell transplant recipients are reviewed. Pediatr Blood Cancer 2007;48:222–226. © 2006 Wiley-Liss, Inc.