Background: Cloprostenol, as a common clinically used PGF2α analogue, is widely employed in veterinary practice to induce parturition. It is main action, as a potent luteolytic, carried by vasoconstriction of the blood vessels that supply the corpus luteum. While vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis. Objective: This study aimed to investigate the precise effects of PGF2α analogue (cloprostenol) on the VEGF gene expression. Methods: Chorioallantoic membrane (CAM) of local chicken fertilized eggs were used at 6 and 9 days of incubation. Control group, without treatment, and other groups treated with (22.5µg/egg) of cloprostenol sodium (Galapan)® and eggs were re-incubated. CAM blood vessels were observed and documented and samples of them were isolated at 1, 2, 4, 6, 12, and 24 hours after incubation. mRNA was isolated and converted to cDNA, and RT-PCR was done to determine the gene expression of VEGF. Results: It shows that the peak of gene expression of VEGF gene was at 24 hours of day 9 of incubation. Furthermore, the best antiangiogenic effects were at the same time of 6 hours of the day 6 of incubation. Conclusion: It could be concluded that PGF2α analogue (cloprostenol) has vasoactive properties depend particularly on the VEGF, this action is in a time-dependent manner and may be based on the hypoxia-induced pathways that elicited by vasoconstrictive action of cloprostenol.