Aim: To discuss an apical accidental extrusion of 2.5% sodium hypochlorite (NaOCl) with assistance of low-level laser. Case Report: A 39-year-old female was referred to the undergraduate clinic and during root canal preparation (RCP) reported an immediate burning sensation, which was accompanied by an acute and severe pain. After 3 hours, the patient returned with persistent spontaneous and severe pain in the area of the maxillary incisor and pronounced swelling in her upper lip. The diagnosis hypothesis was accident with extrusion of NaOCl beyond of apex root. The patient immediately received a single oral dose of 8 mg of corticosteroids, and also was prescribed amoxicilin, and anti-inflammatory. To assist the control of inflammation, low level laser therapy was performed. Results: The patient returned 18 hours after the first appointment and the pain and swelling gradually decreased, and although there was extensive ecchymosis, no skin necrosis was observed. After 4 days, the patient presented no pain and the swelling area had total remission on day 11. The 17 months follow-up showed clinical aspect with normal appearance. Conclusions: The therapy with antibiotics, anti-inflammatory and LLLT for severe tissue damage caused by NaOCl reduced the severe manifestations of pain and edema.