Fluoride is one of the most reactive elements in nature, and commonly used in toothpaste since it helps to prevent cavities. Despite this advantage, excessive ingestion of fluoride can cause acute toxicity and gastric disturbance from hydrofluoric acid that was formed in the stomach. We report a case of previously healthy, 41-month-old girl who visited the emergency department with persistent abdominal pain and hematemesis after ingestion of fluoride-containing toothpaste. Though the ingested dose of fluoride was below the toxic dose, serious symptoms developed. We performed esophagogastroduodenoscopy, and confirmed a hemorrhagic gastritis caused by hydrofluoric acid. The girl was uneventfully discharged on day 3 after receiving conservative care. When managing children who ingested fluoride-containing toothpaste, physicians need to consider their symptoms, not the ingested amount. In addition, parents should be cautious when their children use fluoride-containing toothpaste.