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Background: Angiogenesis is one of the most important biological processes which is characterized by the formation of new blood vessels in many developmental and pathological stages. Therefore, angiogenesis blockage using anti-angiogenic drugs can be effective in treatment of such diseases as hemorrhages and cancers. Citrullus colocynthis (bitter melon) is a medicinal plant with cytotoxicity effects that its anti-angiogenic effects were investigated in this study. Materials and Methods: In an experimental study, at first, Citrullus colocynthis alcoholic extract was prepared. Then, 30 Highline fertilized eggs were randomly divided into control, sham-exposed, and treatment groups. On the seventh day of incubation, the sham-exposed group was treated with normal salin and the treatment group was treated with the plant extract. On the 10th day of incubation, CAMs were examined and photographed by research photostereomicroscope. The number and length of vessels around the treated region were measured and analyzed through SPSS and t-test (p<0.05). Results: According to data analysis, the number (31.40±5.87) and length (46.60±7.33 cm) of vessels in the control group did not reveal a significant difference in comparison to the number (27±5.16) and length (42.40±5.05 cm) of vessels in the sham-exposed group. However, a significant decrease was observed in the number (6.70±2.05) and length (14.79±3.34 cm) of vessels in the treatment group in comparison to the control group(p<0.05). Conclusion: The alcoholic extract of Citrullus colocynthis seems to have had a repressive effect on angiogenesis in chick chorioallantoic membrane. Therefore, it decreases the number and length of vessels around the treated area.