The article aimed to assess the mRNA-expression levels of Interferon-Stimulated Gene 15 (ISG15) in does, both pregnant and non-pregnant, during the early pregnancy period. Additionally, to determine pregnancy detection parameters using the ISG15 mRNA expression pattern. In this study conducted in Al-Saqlawiyah, Al-Anbar governorate, Iraq, 25 does and 5 bucks were utilized from March to October. The estrus induction protocol involved the use of intravaginal sponges containing Medroxy Progesterone Acetate for 12 days along with 500 IU PMSG at the time of sponge withdrawal. Estrus was identified, and the breeding bucks facilitated mating. Pregnancy status was assessed through transabdominal ultrasonography. Blood samples were obtained from does before estrus induction and after mating (on days 15 and 25 post-mating). Subsequently, RNA samples were extracted from peripheral blood leukocytes (PBLs), and ISG15 expression levels were evaluated using Real-Time PCR. The Receiver Operating Characteristic (ROC) curves were used to determine the efficiency of the ISG15 method in pregnancy detection. The results indicated a significantly higher (P≤0.01) expression of ISG15 in pregnant does on both days 15 and 25 compared to the control (before mating) and non-pregnant does during the same periods. Additionally, there were no significant differences observed between the two time frames within each non-pregnant and pregnant group. The ROC curves derived from the RT-PCR data on day 15 demonstrated a higher Sensitivity (Se) and Specificity (Sp) of 90% and 100%, respectively, with a dependable cutoff value >3.15. Moreover, on day 25, the ROC curves recorded 100% Se and 80% Sp at the designated cutoff point of >1.5. In summary, ISG15 exhibited a significant upregulation exclusively in pregnant does, while displaying only slight changes in mated/non-pregnant does. Due to its high accuracy in predicting pregnancy, it can serve as a reliable method for detecting implantation and early pregnancy in does.