The prevalence of nonsuicidal self-injury (NSSI) in adults is lower than that in adolescents and it is more prevalent in patients with psychiatric disorders. Sleep disturbances such as nightmares are associated with NSSI after accounting for depression; thus, persons with major NSSI sometimes present at medical institutions during the night seeking emergency treatment. Gingival tissues comprise the most frequent target of self-injury of the oral cavity using oral hygiene tools. Most NSSI in the oral cavity is minor because such tools are blunt. Major NSSI such as autoamputation of the tongue is rare. We describe two patients who partially autoamputated the apex of their own tongues using edged tools. Case 1 was a 55-year-old female with depression who had defaulted from psychiatric intervention. She had cut off her tongue using a Japanese kitchen knife and presented with the dry, necrotic amputated portion and blood oozing from the remainder of her tongue. We debrided and sutured the remainder of the tongue without reattaching the amputated portion. Her postoperative course was uneventful, and she was free of adverse events such as functional disability and wound infection. Case 2 was a 69-year-old female with schizophrenia who had defaulted from psychiatric intervention and had cut off her tongue using scissors. The amputated portion of the tongue was lost and the remainder, which was oozing blood, was debrided and sutured. She defaulted on a follow-up appointment. Neither of these patients had suicidal intent. The prevalence of NSSI across all age groups has recently increased, and the risk that self-injury will become normalized has become a concern. Thus, dentists as well as oral and maxillofacial surgeons should be aware of the possibility that patients will present with major NSSI requiring emergency treatment.