<b><i>Background:</i></b> Posterior reversible encephalopathy syndrome (PRES) is a rare but serious complication after allogeneic hematopoietic stem cell transplantation (alloHSCT). Among others, calcineurin inhibitors (CNI) for prophylaxis of graft-versus-host disease (GvHD) may promote the development of PRES, but the pathomechanism is still controversial. Discontinuation of CNI facilitates remission of symptoms but might contribute to the unfavorable prognosis of PRES due to an elevated incidence of GvHD. <b><i>Methods:</i></b> This is a case series of 7 patients with PRES from a retrospective analysis of 146 consecutive patients who received alloHSCT for hematologic malignancies. <b><i>Results:</i></b> At the onset of PRES, all patients presented a systemic infection, while no influence was seen for underlying disease, conditioning regimen, donor type, or GvHD. Discontinuation of CNI and control of the blood pressure reversed neurological symptoms in 6 patients, while 1 patient died from septic multiorgan failure. After bridging with prednisolone and/or mycophenolic acid, replacement of CNI by the mammalian target of rapamycin (mTOR) inhibitor everolimus effectively prevented severe GvHD without recurrence of PRES. <b><i>Conclusions:</i></b> A systemic infection/inflammation may be an important cause of PRES. Prophylaxis of GvHD by the mTOR inhibitor everolimus in case of PRES after alloHSCT demonstrated promising results but needs to be validated in larger cohorts.