Rectal prolapse (RP) most commonly occurs among elderly women and is caused by vulnerable suspensory tissue in the pelvis. In Japan, the Gant-Miwa-Thiersch procedure (GMT) is recommended for elderly people with poor general health. We retrospectively analyzed clinical data from 12 patients who underwent GMT at our hospital from September 2005 to July 2021 and investigated the effect of GMT on the mesorectum using abdominal-pelvic computed tomography (CT) performed for other diseases. The median age of the cohort was 82 years, and 92% of the subjects were women. The median RP length was 5 cm, and the median follow-up period was 60 months. Recurrence was observed in 1 of 12 patients (8.0%). CT conducted before and more than 6 months after GMT revealed no abnormal findings in the mesorectum, whereas CT within 5 months after GMT revealed hyperdense fat in the mesorectum in all three patients (100%; P < 0.05). The RP recurrence rate after the GMT was low. The mechanism of the effect of GMT may involve not only a direct mucosal plicating effect but also adhesional rectosacral fixation due to the presence of inflammation extending to the mesorectum.