Background: Intrauterine Growth Restriction (IUGR) is defined as decreased fetal birth weight less than 10^th percentile as regard to gestational age also diagnosed when there is a delay more than 2 weeks in a serial ultrasound monitoring of fetal gestational age. Objective: The aim of the work was to evaluate accuracy of transcerebellar diameter (TCD) in detection of gestational age in pregnancies with intrauterine growth restriction IUGR. Patients and Methods: Case-Control study was carried out on 52 women with normally progressing pregnancies during the third trimesters, with gestational ages between 27 and 37 weeks of gestation came to outpatient clinic of department of Obstetrics and Gynecology, Zagazig General Hospital and Zagazig University Hospital from June 2019 to March 2020, of them, 26 subjects were normal pregnancies and 26 subjects diagnosed as IUGR in 3^rd trimester at gestational age (27week to 37 week). Trans-abdominal ultrasound was performed on all subjects; Fetal TCD was measured using the widest diameter of the cerebellum, measurement of fetal Bi-Parietal Diameter (BPD), Abdominal Circumference (AC), and Femur Length (FL). Results: There was statistically significant difference between gestational age (GA) by Last Menstrual Period (LMP) and sonar parameters at normal group but highest was TCD with P value 0.000 but in IUGR group only TCD, AC and FL were significantly positive correlated with GA; and TCD were highly significant. Conclusions: It could be concluded that the TCD measurement appears to be an accurate predictor of gestational age, even in the third trimester of pregnancy.