Transanal total mesorectal excision (TaTME) refers to endoscopic retrograde total mesorectal excision and is becoming increasingly popular worldwide. TaTME improves surgical manipulation and minimizes the risk of local recurrence of rectal cancer by ensuring circumferential resection margins. TaTME is mainly indicated for patients in whom transabdominal approaches are expected to be technically challenging. We extended the indications for TaTME to include surgery for ulcerative colitis lesions that might be cancerous in the rectum. Here, we report a case of proctocolectomy with TaTME for ulcerative colitis. A 38-year-old woman who was receiving treatment for ulcerative colitis underwent a biopsy for random samples from the transverse colon to the rectum. Histopathological findings revealed noninvasive dysplasia with p53 overexpression, suggestive of cancer. We extended the indication of TaTME to surgery for ulcerative colitis. We formed two surgical teams and performed laparoscopic proctocolectomy with TaTME simultaneously. This simultaneous operation reduced the duration of the procedures in the present case. The patient was discharged without any complications and underwent loop ileostomy closure four months postoperatively. The patient recovered without significant loss of the anal sphincter function and is doing well four months after the second surgery. We propose laparoscopic proctocolectomy with TaTME to be conducted simultaneously by two teams as a safe and effective technique that is associated with a shorter operation time than that reported previously. Additionally, TaTME was useful in confirming the appropriate dissection layer as well as in surgical manipulation. Hence, TaTME could serve as a useful therapeutic option for ulcerative colitis surgery.