A case of retrograde intussusception is presented occurring >1 year following a Roux-en-Y gastric bypass (RYGBP). Presentation may be confusing and lead to a serious delay in diagnosis. Review of the literature shows most intussusceptions following RYGBP are retrograde, and most, if not all, appear to originate in the proximal common channel, as ours clearly did. The average excess body weight loss in these patients is much higher than expected, adding evidence that a dysmotility disorder is involved. A hypothesis is presented regarding the mechanism involved in these retrograde intussusceptions.