The uterus with rudimentary horn occurs as a result of a lack of development during fetal life of the middle and lower parts of one of the Miillerian ducts, in which there is a failure of fusion of the two ducts, The incidence of this uterine anomaly is rare. Many cases of rudimentary uterine horn are not discovered since they do not become involved in a pregnancy, and thus remain symptomless and uncomplicated, and the diagnosis usually being made only with pregnancy with rupture. In this presentation, we describe a case of diagnosis and management of unruptured non-communicating rudimentary uterine horn pregnancy at the third trimester. The patient diagnosed by ultrasonography and MRI, was hospitalized for further evaluation and delivery under the impression of unruptured non-communicating rudimentary horn pregnancy. A living male infant weighing 1,930 gm was delivered by cesarean section at 33+l weeks due to impending preterm labor. Some articles concerned this subject were reviewed briefly to discuss relevant method of diagnosis, treatment, and clinical characteristics.