Laser powder bed fusion (L-PBF) enables the creation of advanced metal parts that are difficult to manufacture conventionally. In this study, the model parameters of the Johnson–Cook (JC) constitutive relation and the damage parameters of the JC failure model for 1.2709 steel produced via L-PBF were determined. Constitutive parameters were identified from quasi-static uniaxial tensile tests conducted on smooth specimens. In contrast, stress triaxiality-dependent damage parameters were determined using tensile tests on notched round bar specimens in combination with FEM simulations. The load–displacement curves showed good agreement with the experimentally obtained data. The strain–rate–dependent failure model parameter was determined by correlating Charpy impact test results with numerical simulations. Reasonable agreement between the simulation and experimental results was achieved. The results demonstrate that the proposed experimental–numerical framework provides a reliable basis for modelling both the quasi-static and impact fracture behaviour of L-PBF-fabricated 1.2709 steel.