The present study reviewed cases of Toxic megacolon (TM) treated in our department, summarized the timing and technique of surgery, and considered key points for surgical management. This single-center retrospective study included the medical records of patients clinically diagnosed with TM who underwent surgery between 1985 and 2020. The diagnostic criteria and screening scores for sepsis, such as the systemic inflammatory response syndrome (SIRS) criteria, quick Sequential Organ Failure Assessment (qSOFA) score, and Modified Early Warning Score (MEWS), were validated. The preoperative clinical features and perioperative findings were also investigated. There were eight male and six female patients. Nine patients (64.3%) satisfied the criteria for toxemia proposed by Narabayashi, and 10 patients (71.4%) fulfilled the SIRS criteria. A positive qSOFA score was confirmed in 1 patient (7.1%). The MEWS was high in 2 patients (14.3%). Intestinal perforation occurred in 2 patients (14.3%), and 1 of them died from disseminated intravascular coagulation. The mortality rate of TM with perforation was 50%. Eleven patients (78.6%) underwent total colectomy with end ileostomy. TM does not have well-defined diagnostic criteria, in addition to developing sometimes as borderline or fulminant cases, and must be recognized at an early stage, taking various findings into consideration. The criteria proposed by Narabayashi and the SIRS criteria, which met in a high percentage of our cases, are recommended as indicators for determining the toxicity of TM. It is also important to consider surgery in the early stages of TM, even if clinical findings do not meet all the criteria.