The effect of silver nanoparticles (Ag NPs) at oral administration on the gastric mucosa of intact animals and possible prevention of acute gastric ulcer formation has been studied. The indices of nonspecific proteinases and their inhibitors in blood serum and the supernatant of gastric mucosal homogenate were evaluated. It has been established that the use of Ag NPs solution as a drinking substrate in intact animals is accompanied by a minimal reaction of the components of proteinase inhibitory systems both at the systemic and local levels. Prophylactic use of Ag NPs solution in modeling acute gastric ulcers leads to inhibition of activation of nonspecific proteinases and preservation of inhibitory potential, which may indicate the presence of anti-inflammatory effects of Ag NPs. The inhibition of the activation of proteolytic enzymes and the preservation of a sufficiently high inhibitory potential of the Ag NPs solution as a preventive means for the formation of an ulcerative defect of the gastric mucosa indicates the presence of anti-inflammatory effects of Ag NPs, which is the basis for further research.