An 89-year-old woman was referred to our division for management of her rectal prolapse, characterized by a 9-year history of gradually worsening severe anal pain. At rest, the rectal prolapse measured 16 cm. Vaginal prolapse was not observed. She was diagnosed with a high take-off prolapse and underwent a laparoscopic ventral mesh rectopexy (LVR) combined with postero-unilateral dissection and mesorectal promontofixation. A deep Douglas’ pouch and a highly stretched mesorectum around the sacrum were observed intraoperatively. The promontory peritoneum was incised to gain access to the presacral space. Then, an inverted J-shape incision was made, with posterior dissection of loose connective tissue that developed caudally beyond the level of lateral ligament. The right lateral ligament was preserved. After fixing the LVR mesh to the promontory, the mesorectum on the right side of the rectum was secured to the L5S1 anterior longitudinal ligament using a non-absorbable suture. The total operating time was 156 min, and the estimated blood loss was 20 ml. No postoperative complications, including constipation and recurrence, were observed five months later. This study highlights that, in LVR, severe rectal prolapse may require further fixation of the rectum or mesorectum around the promontory to prevent high take-off recurrence. Postero-unilateral rectal dissection and mesorectal suture promonotofixation are simple and feasible procedures that may be combined with LVR.