Ocimum sanctum, a holy plant is used by many traditional medical practitioners for various diseases in day to day life. This holy plant- Tulsi is used in the present investigation for study of its angiogenesis efficiency. The effect of acetone extract of O. sanctum leaves was studied by using chick chorioallantoic membrane (CAM) assay in ovo. The angiogenesis was studied after 48 hrs, 72 hrs and 96 hrs treatment chick embryos after day 6. The morphometry and histology was studied during this investigation. There was notable reduction in number of secondary and tertiary blood vessels along with reduction in their diameter as compared to that of in normal CAM. It is due to inhibition of angiogenic factors or due to cellular apoptosis. Angiostatic property of acetone extract of leaves support anti-cancerous ethnomedicinal property of this plant and paves the foundation to synthesize the drug against tumor.