The paper presents an experimental investigation of the ductile fracture of specimens with different circumferential notches. Specimens made from ENAW_2024-T351 aluminum alloy were subjected to non-proportional tension–torsion loading. The tests were carried out on an MTS testing machine coupled with the ARAMIS 3D 4M vision measuring system, enabling simultaneous non-contact tracking of the elongation and torsional angle of the measurement base. Depending on the assumed notch radius and the non-proportionate load scheme, the critical tensile force and torsional moments that caused the fracture initiation of the specimen were determined. A significant effect of load configurations and notch radius on the shape of the fracture surface as well as the fracture mechanisms causing the failure of specimens was demonstrated. The equation describing the configuration of critical loads for specimens with different notch radii was applied.