Structures should adhere to capacity and serviceability requirements that can be compromised by dynamic excitation. Structural vibration mitigation aims to ensure serviceability and guarantee safety, but often suffers from limitations of the enabling devices; usually preferred to follow a passive scheme. The current study harnesses the potential of nonlinear mechanisms to amplify the vibration mitigation effects. A geometrically nonlinear device is proposed, called NegSV, which is mounted on a frame structure, without requirement of an additional tunable mass mechanism. The nonlinear configuration l eads t o n egative stiffness phenomena, which can be exploited for guiding the input energy toward specific structural elements. The dynamics of the system and its efficacy in terms of vibration attenuation is studied via nonlinear finite element analyses under base e xcitation. The seismic input is additionally parametrized in order to allow for a probabilistic assessment of its influence o n t he performance of the device, via use of Monte Carlo simulations. The probabilistic distributions of associated structural integrity metrics are calculated on the basis of assumed distributions of the input parameters. The respective results for both the unprotected and protected structures are compared, revealing effective vibration mitigation potential for critical system components, such as the base of the structure, relieving base shear. 1016COMPDYN 2023 9 th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis (eds.