Aneurysm rupture is a life-threatening event, yet its underlying mechanisms remain largely unclear. This study investigated the fracture properties of the thoracic aneurysmatic aorta (TAA) using the symmetry-constraint Compact Tension (symconCT) test and compared results to native and enzymatic-treated porcine aortas’ tests. With age, the aortic stiffness increased, and tissues ruptured at lower fracture energy. Patients with bicuspid aortic valves were more sensitive to age, had stronger aortas and required more than tricuspid valves individuals (peak load: axial loading 4.42 1.56 N vs 2.51 1.60 N; circumferential loading 5.76 2.43 N vs 4.82 1.49 N. Fracture energy: axial loading 1.92 0.60 kJ m-2 vs 0.74 0.50 kJ m-2; circumferential loading 2.12 2.39 kJ m-2 vs 1.47 0.91 kJ m-2). Collagen content partly explained the variability in, especially in bicuspid cases. Besides the primary crack, TAAs and enzymatic-treated porcine aortas displayed diffuse and shear-dominated dissection and tearing. As human tissue tests resembled enzymatic-treated porcine aortas, microstructural degeneration, including elastin loss and collagen degeneration, seems to be the main cause of TAA wall weakening. Additionally, a tortuous crack developing during the symconCT test reflected intact fracture toughening mechanisms and might characterize a healthier aorta.