Introduction: Eating disorders which embrace anorexia nervosa, bulimia nervosa, and eating disorders not otherwise specified can be life-threatening due to general medical complications; however, the diagnosis of eating disorder is often delayed due to a low suspicion index. Gastroenterologists are health care providers who may come into contact with patients with undiagnosed eating disorders; it has been previously demonstrated that patients with eating disorders frequently have a significant association with functional dyspepsia. Signs of dental erosion have been described in patients with eating disorders; hence, they may help to identify eating disorders in patients who present with functional dyspepsia and deny having an eating disorder. Case presentation: In this report we describe three cases (a 25-year-old white woman, a 24-year-old white woman, and a 40-year-old white man) with undiagnosed eating disorders, in which a more comprehensive approach, such as the recognition of dental erosion joined with a careful gastrointestinal investigation, was performed to reach a final diagnosis of an eating disorder. Conclusions: The screening for dental erosion in patients seeking or receiving medical treatment for dyspeptic symptoms in a gastrointestinal out-patient clinic could be an aid for gastroenterologists to recognize the presence of an underlying eating disorder. A close collaboration with dentists, in addition to psychiatrists, could provide a more favorable treatment outcome.