Patients with Marfan syndrome used to succumb early in life from cardiovascular complications. With the current rapid advance in medical and surgical care, such patients may now have near-normal longevities. Consequently, rare late-life complications are emerging in these patients and represent challenges to clinicians for their diagnoses and treatments. The authors report a rare case of pelvic pain and genital prolapse from a giant presacral Tarlov cyst in a 67-year-old patient with Marfan syndrome., This 67-year-old Caucasian female presented with progressively severe pelvic pain, intermittent explosive diarrhea, and dysuria. Physical and bimanual examination demonstrated genital prolapse and a nontender, cyst-like mass fixed in the midline. She underwent ultrasound, CT, and eventually MRI evaluations that led to the diagnosis of a giant (6.7 x 6.4 x 6.6 cm) Tarlov cyst originating from the right S-2 nerve root sleeve/sacral foramen with intrapelvic extension. She underwent S1-S2 and S2-S3 laminectomy with obliteration of the Tarlov cyst using aneurysm clips. Postoperatively, her pelvic pain and bowel symptoms resolved and the bladder symptoms improved. The 3-month follow-up CT of abdomen/pelvis demonstrated resolution of the cyst. The present case illustrates that clinicians caring for elderly patients with Marfan syndrome need to increasingly recognize such unusual late-life complications. Also, these large Tarlov cysts can be simply and effectively obliterated with aneurysm clips.