Due to their immunocompromised state, recipients of hematopoietic stem cell transplants (HSCTs) are at a higher risk of opportunistic infections, such as that of toxoplasmosis. Toxoplasmosis is a rare but mortal infection that can cause severe neurological symptoms, including confusion. In immunosuppressed individuals, such as those with acquired immunodeficiency syndrome (AIDS), toxoplasmosis can cause movement disorders, including hemichorea–hemiballismus. We present the case of a 54-year-old Caucasian male with a history of hypertension and JAK-2-negative primary myelofibrosis who underwent an allogeneic peripheral blood stem cell transplant from a related donor. After the development of acute changes in mental status, left-sided weakness, and left-sided hemichorea–hemiballismus post-transplant, the patient was readmitted to the hospital. Subsequent testing included an magnetic resonance imaging (MRI) of the brain, which revealed multiple ring-enhancing lesions around the thalami and basal ganglia, as well as a cerebrospinal fluid tap that tested positive for toxoplasmosis. The patient was initially treated with intravenous clindamycin and oral pyrimethamine with leucovorin. The completion of treatment improved the patient’s mental status but did not improve his hemichorea–hemiballismus. This case illustrates an uncommon complication associated with central nervous system (CNS) toxoplasmosis in stem cell transplant recipients. Due to its rarity, cerebral toxoplasmosis in immunocompromised patients often remains undetected, particularly in HSCT patients who are immunosuppressed to improve engraftment. Neurological and neuropsychiatric symptoms due to toxoplasmosis may be misidentified as psychiatric morbidities, delaying appropriate treatment. Polymerase chain reaction (PCR) assays offer methods that are sensitive and specific to detecting toxoplasmosis and provide opportunities for early intervention.