Rudimentary uterine horn pregnancy is rare and, to our knowledge, has not been previously reported in Cameroon. We herein report the case of a 22 year old second gravida referred for acute abdominal pain at 17 weeks of gestation. Physical examination revealed hemoperitoneum with hypovolemic shock. After resuscitation, an emergency exploratory laparotomy was done and we found hemoperitoneum of 3,500 milliliters, a bicornuate uterus with a ruptured right rudimentary communicating horn containing a non viable foetus. There were no other abnormalities. We performed an excision of the rudimentary horn with ipsilateral salpingectomy. Post-operative course was uneventful and the woman was discharged seven days later. This case emphasizes the importance of good antenatal care to avoid complications.