Objective: Our aim was to analyze brain MRI findings in pediatric patients who developed neurologic complications after allogeneic bone marrow transplantation. Materials and methods: This prospective study included 33 consecutive patients (age range from 3 to 18 years, mean 11.8 ± 5.1 years). They were referred to the MRI unit because of the neurological symptoms in the post transplant period. The underlying disorders included: non malignant hematological disorders (n = 20, 60.6%) and hematological malignancies (n = 13, 39.4%). Onset of the presentation of the complication in relation to the chronology of the transplant was identified in each patient (phase1: from days 0 to 30, phase 2: from days 30 to 100, and late phase after day 100). Results: According to the MRI findings 6 patients (18.2%) showed normal examinations. Twentyseven patients (81.8%) with positive MRI findings, are grouped into 7 main categories: posterior reversible encephalopathy syndrome (n = 16, 48.48%), intracranial hemorrhage (n = 2, 6.06%), cerebral venous sinus thrombosis (n = 1, 3.03%), CNS infection (n = 2, 6.06%), leukoencephalopathy (n = 5, 15.15%), mild atrophy (n = 11, 33.33%), CNS relapse (n = 1, 3.03%), with 9 patients having more than one diagnosis. Ten cases of PRES and 1 case of sinus thrombosis were detected in phase 1. Two cases of PRES and 2 cases of intracranial hemorrhage were detected in phase 2. Four cases of leukoencephalopathy, 4 cases of PRES, 2 cases of CNS infection, and 1 case of CNS relapse were detected in phase 3.Conclusion: CNS complications after allogenic BMT in pediatric patients could cause a significant clinical problem. MRI can provide early diagnosis and follow-up to monitor treatment changes. Knowing the onset of the presentation of the complication in relation to the chronology of the transplant is important as it provides significant guidance on which causes to consider.