Background: Acquired demyelinating syndromes (ADS) in children are a group of distinct first immune-mediated demyelinating events of the central nervous system (CNS). Predictive biomarkers for future diagnosis are lacking. A putative target antigen is myelin oligodendrocyte glycoprotein (MOG). We analyzed the presence of MOG antibodies in a cohort of ADS patients in The Netherlands. Methods: Using a cell-based assay, we analyzed 117 children with ADS from a nationwide cohort, whom were divided into five groups: optic neuritis (ON; n = 20), transverse myelitis (TM; n = 7), other monofocal ADS ( n = 22), polyfocal ADS without encephalopathy ( n = 44) and polyfocal ADS with encephalopathy ( n = 24). Additionally, we tested children with other neurological diseases (OND; n = 13), healthy children ( n = 31) and adult polyfocal ADS plus encephalopathy (ADEM) patients ( n = 29). Results: We found that 21 of the 117 children with ADS tested anti-MOG seropositive (18%). The group of patients with ADEM had the highest prevalence of anti-MOG seropositivity (42% versus 18% in the non-encephalopathic polyfocal ADS patients). Although 47 ADS children had a final diagnosis of multiple sclerosis (MS), in only one of them were MOG antibodies detected (2%), with only borderline positivity. Only 1 out of the 29 adult ADEM patients tested anti-MOG seropositive. Conclusions: MOG antibodies are strongly skewed towards ADS children that present with an ADEM-like disease onset. The presence of such antibodies pleads against a future diagnosis of MS.