Toxoplasmosis is a rare but well recognized opportunistic infection that can occur after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Besides encephalitis, other common presentations of Toxoplasma gondii infection are interstitial pneumonitis and myocarditis. Because of its non-specific clinical and biological signs and its lethal outcome, toxoplasmosis is often misdiagnosed and only revealed at autopsy. We report a case of a postmortem diagnosis of disseminated toxoplasmosis associated with hemophagocytic syndrome, which underlines the value of necropsy in cases of death after transplantation. We also discuss clinical presentations and risk factors that lead to toxoplasmosis in allo-HSCT recipients.