US is increasingly performed in Crohn disease (CD) in children as a first line imaging modality. It reduces the use of other more invasive examinations such as endoscopy, CT or contrast enema. We describe bowel ultrasonography technique, normal bowel appearances on US and pathological patterns in CD. We discuss the current role and limitations of bowel US in CD in children including diagnosis, extent of disease, assessment of disease activity, follow-up and detection of complications. The diagnostic accuracy of US is discussed according to the literature and compared to other imaging modalities. US is currently used for screening in children with the suspicion of inflammatory bowel disease (IBD) with a good negative predictive value. In follow-up, US has a role in monitoring medical treatment by evaluating disease activity, extent of disease and for detecting complications.