A 66-year-old woman with refractory angioimmunoblastic T-cell lymphoma underwent cord blood transplantation. Prior to transplantation, a serological test for Toxoplasma gondii-specific IgG antibodies was positive. On day 96, she exhibited fever and dry cough. Chest CT showed diffuse centrilobular ground glass opacities in both lungs. The reactivation of T. gondii was identified by the presence of parasite DNA in peripheral blood and bronchoalveolar lavage fluid. Moreover, brain MRI revealed a space occupying lesion in the right occipital lobe. Therefore, disseminated toxoplasmosis was diagnosed. She received pyrimethamine and sulfadiazine from day 99. The lung and brain lesions both showed improvement but the PCR assay for T. gondii DNA in peripheral blood was positive on day 133. On day 146, she developed blurred vision and reduced visual acuity, and a tentative diagnosis of toxoplasmic retinochoroiditis was made based on ophthalmic examination results. As agranulocytosis developed on day 158, we decided to discontinue pyrimethamine and sulfadiazine and the treatment was thus switched to atovaquone. Moreover, we added spiramycin to atovaquone therapy from day 174, and her ocular condition gradually improved. In general, the prognosis of disseminated toxoplasmosis after hematopoietic stem cell transplantation (HSCT) is extremely poor. However, early diagnosis and treatment may contribute to improvement of the fundamentally dismal prognosis of disseminated toxoplasmosis after HSCT.