A significant role of the stress response to many different diseases prompted a search for new specialized and non-specialized anti-stress agents. This study examines the effect of the compound L17 from the group of 5-phenyl substituted-6H-1,3,4-thiadiazine-2-amines, on the manifestations of the stress response. The authors used a standard model of immobilization stress, in which an animal was immobilized on its back for 6 h a day. Parameters of the morphological and functional states of the organs studied were measured and biochemical and enzyme-immunoassays were carried out on the first and second days. This study reveals that the main mechanism by which the L17 compound mediates of its anti-stress was by activation of macrophages on the second day of the experiments and the inhibition of apoptosis in the thymus. The results enable us to suggest that the compound L17 does not improve resistance to stress; however, it does lower the reaction to stress.