Treatment of acquired rectovesical or rectourethral fistula can be very challenging for surgeons. When a conservative approach fails, complex surgery is needed, with a substantial probability of complications and recurrences. In order to minimize the need for major surgery, autologous mesenchymal stem cells have been used to treat fistulas, especially in patients with inflammatory bowel diseases. We present a case of a patient with an iatrogenic rectovesical fistula that was successfully treated with transanal infiltration of mesenchymal stem cells around the rectal orifice of the fistula.