To evaluate the neurodevelopmental outcome at school age in children newly diagnosed with fetal neonatal alloimmune thrombocytopenia (FNAIT). This observational cohort study included children diagnosed with FNAIT between 2002 and 2014. Children were invited for cognitive and neurological testing. Behavioral questionnaires and school performance results were obtained. A composite outcome of neurodevelopmental impairment (NDI) was used, defined and subdivided into mild-to- moderate and severe NDI. Primary outcome was severe NDI, defined as IQ < 70, cerebral palsy with Gross Motor Functioning Classification Scale (GMFCS) level ≥ III, or severe visual/hearing impairment. Mild-to-moderate NDI was defined as IQ 70-85, minor neurological dysfunction or cerebral palsy GMFCS level ≤ II or mild visual/hearing impairment. In total, 44 children were included at a median age of 12 years (range 6-17 years). Neuroimaging at diagnosis was available in 82% (36/44) of children. High-grade intracranial hemorrhage (ICH) was detected in 14% (5/36). Severe NDI was detected in 7% (3/44); two children had high-grade ICH and one low-grade ICH and perinatal asphyxia. Mild-to- moderate NDI was detected in 25% (11/44); one child had high-grade ICH and eight were without ICH, yet for two children neuroimaging was not performed. Adverse outcome (perinatal death or NDI) was 39% (19/49). Four children (9%) attended special needs education, three of whom had severe NDI and one with mild-to-moderate NDI. Total behavioral problems within the clinical range were reported in 12%, which is comparable with 10% in the general Dutch population. Children who are newly diagnosed with FNAIT are at increased risk for long- term neurodevelopmental problems, even those without ICH.