Previous studies of adults have shown protective associations between clinical recognition of a mental disorder in the emergency department and short-term risk of repeat self-harm. Similar studies of young self-harm patients are lacking. We conducted a retrospective longitudinal cohort analysis of national Medicaid claims data in patients aged 10–19 years with self-harm who were discharged from emergency departments to the community (N = 2,703). Emergency department mental disorder recognition was not associated with a significant change in repeat self-harm visits during the 30-day follow-up period. Future studies should assess whether other aspects of emergency care influence short-term risk of repeat self-harm.