Background <p>Self-induced vomiting (SIV) in patients with eating disorders exposes the oral cavity to repeated chemical and mechanical insults, leading to various oral complications. Necrotizing sialometaplasia (NS) is one such complication; however, most cases resolve spontaneously and follow a benign course without requiring surgical intervention.</p> Case presentation <p>A woman in her twenties with a long history of an eating disorder characterized by habitual SIV developed NS of the hard palate. Unlike the usual benign course, the lesion failed to heal spontaneously and progressed to a palatonasal fistula. Her clinical course was notable for several behavioral and clinical factors that may have contributed to sustained local irritation of the palatal tissues, such as persistent vomiting, smoking, and dental procedures requiring local anesthesia. Multidisciplinary psychiatric and dental management was provided throughout the clinical course. Since spontaneous closure of the fistula could not be expected, surgical repair was ultimately performed.</p> Conclusions <p>Although NS associated with SIV in patients with eating disorders is usually benign and self-limiting, it can rarely progress to severe and irreversible oral complications such as a palatonasal fistula. Despite the fact that NS is not life-threatening, its severe progression can significantly impair quality of life. Accumulating clinical experience with such hidden complications may improve the quality of psychoeducation and advance the treatment of eating disorders.</p>