The goal of this study was to determine the ideal period for sexing Boer goat fetuses using transrectal ultrasonography. The objective of Experiment 1 was to diagnose the sex of fetuses based on the final position of the genital tubercle (GT) through a series of daily exams between Days 40 and 60 of pregnancy. The objective of Experiment 2 was to evaluate the accuracy of fetal sexing with a single exam conducted between Days 45 and 60 of pregnancy. The transrectal exams were conducted using a dualfrequency, linear-array transducer (6.0 and 8.0 MHz). In Experiment 1, 61 fetuses were monitored at 24-hour intervals between Days 40 and 60 while 47 fetuses were examined only once between Days 45 and 60 in Experiment 2. The accuracy of fetal sexing in Experiment 1 was 100% (8/8) for single pregnancies, 96.9% (31/32) for twin pregnancies, and 100% (21/21) for triplet pregnancies. In Experiment 2, the accuracy was 94.4% (17/18) for single pregnancies, 80.8% (21/26) for twin pregnancies, and 100% (3/3) for triplet pregnancies. There was no difference in accuracy between the distinct type of pregnancy and between the two experiments (98.3% and 87.2% for Experiment 1 and 2, respectively). The GT migration occurred between 43 and 54 days of pregnancy (mean = 47.4 ± 6.5 days). In conclusion, the use of ultrasound for sexing goat fetuses is a suitable and accurate method based on the final location of the GT and the identification of external genitalia from Day 55 of pregnancy onwards. Daily exams do not increase the accuracy of fetal sexing diagnosis in Boer goats.