Pathogens are a major threat of plant-based production. Expanding restrictions for the use of classical pesticides is increasing the need of alternative applications to control plant diseases. Nanoparticles have recently received increasing research interest as a potential means to protect plants from adverse conditions including pathogen attack. To assess the beneficial potential of silver nanoparticles to protect plants against the bacterial pathogen Pseudomonas syringae, of which numerous economically relevant pathovars are known, we evaluated the effect of silver nanoparticle pre-treatment in the model pathosystem Arabidopsis thaliana–P. syringae. For this purpose, A. thaliana leaves were treated with different silver nanoparticle concentrations prior to P. syringae infection and visible alterations of the leaf tissue in relation to the individual and combined treatments were scored. While treatment with silver nanoparticles in the concentration range between 0.5 and 10 ppm suppressed P. syringae symptom development, concentrations above 5 ppm caused necroses and chloroses in a dose-dependent manner. This indicates that silver nanoparticles affect plant physiological processes related to cell and tissue integrity that are also associated with the development of infection symptoms caused by P. syringae. Therefore, silver nanoparticle treatments in a suitable concentration range support the maintenance of tissue integrity during pathogen infection in combination with their antimicrobial activity, thus preventing loss of biomass. This makes silver nanoparticles a promising tool for integrative crop protection strategies in commercial production.