A unique case of triplet pregnancy in a woman with uterus didelphys is described, with fetuses A and B in the right uterine horn and fetus C in the left horn. Missed abortion of fetus A was diagnosed in the 22nd week of gestation by real-time ultrasonography, but only in the 27th week of gestation did the right uterine horn contract, resulting in expulsion of fetus A. Fetus B was delivered by cesarean section 2 hours later. Fetus C remained in the left uterine horn until the 37th week of gestation, when a viable 2490-g female infant was delivered by cesarean section. Triplet pregnancy occurs with sufficient frequency to be unremarkable; however, triplet pregnancy in a patient with uterus didelphys and with 72 days' lapse between the delivery of the first 2 fetuses and delivery of the third is a rare occurrence.