The aim of this study was evaluate the effects of Bracken fern (BF) (Pteridium aquilinum (L.) Kuhn.) on biological systems. When consumed by animals can cause acute intoxication, hematuria, biochemistry alterations and cancer. To humans the toxicity is associated with its intake on contaminated ground water or milk and inhalation of its spores. In order to check the BF aqueous extract (AEB) deleterious effects on animals blood vessels system, chick embryo chorioallantoic membrane (CAM) was used. It were applying on CAM 0.1, 0.5, 1, 5, 10 e 15 µg/mL of AEB and saline as control. The angiogenesis was analyzed and the vascular density index (VDI) calculated. The CAM samples were prepared and stained with H&E to evaluation of microvessels, Masson’s trichrome to characterize collagen and fibrin deposition and Picro-sirius used to evaluate collagen using polarized light. Also the morphological aspects of embryos were analysed. We observe on the results of neovascularization that AEB did not change significantly the number of vessels/mm², however, membranes treated with AEB (5 or 10 µg/mL) exhibit opacity and tissue fibrosis, both signs of inflammation. Histological analysis with Masson's trichrome and picro-sirius on tissues exposed to AEB respectively has shown increased collagen fibers and presence of fibrilar collagen. The embryos exposed to concentrations of 5 or 10 µg/mL AEB, showed changes as poor face formation and poor closing of abdominal wall. The highest concentration of AEB (15 µg/mL) was lethal to embryos. Although significant effects on the CAM’s vasculature has not observed, tissue aggression was detected, a desmoplasia (an extensive inflammatory signal triggered by tissue injury), changes caused on embryos as well as the presence of toxic substances in the AEB show us an important and deleterious pathway of this bracken fern extract on its intoxicants effects on humans and animals, and even cancer or the death of animals.