Because of the increase of intestinal diseases in humans and animals, caused by Campylobacter jejuni and their increasing resistance to antibiotics, a number of alternative strategies for controlling infections and reducing the presence of bacteria have been proposed. One of the new alternative strategies for control and reduction of thermotolerant species C. jejuni in the gastrointestinal tract of chickens includes the addition of probiotic bacteria, which also include Bacillus subtilis. These interactions between bacteria in the intestines of humans and animals are poorly researched. We studied interactions between C. jejuni and B. subtilis in co-culture and co-adhesion under various conditions and evaluated the number of colony units in the mono-culture and co-culture of both bacteria. The co-cultivation C. jejuni and B. subtilis did not affect the growth of B. subtilis, but it affected the growth of C. jejuni. Co-cultivation in conditions that allow campylobacter growth (microaerophilic atmosphere, 37 °C or 42 °C), reduced the survival of C. jejuni. On the other hand, co-cultivation in the conditions that are not optimal for the growth of campylobacter (aerobic atmosphere, 20 °C or 37 °C), had a protective effect on their survival. Co-adhesion C. jejuni and B. subtilis also affected the adhesions of C. jejuni on the abiotic polystyrene surface, as it reduced the number of adhered campylobacters. We also evaluated intracellular oxidation by monitoring the formation of ROS, the activity of bacterial cells via luminescence of the present ATP and the influence of the spent medium B. subtilis on the membrane integrity of C. jejuni. The increased formation of ROS and consequently higher oxidative stress was in the co-culture of bacteria. In this case, the activity of co-culture decreased only under certain conditions. We discovered, that the spent medium of B. subtilis reduced the membrane integrity of C. jejuni, but had a minor effect on the reduction of C. jejuni. By experiment, we have demonstrated that B. subtilis can reduce the presence of C. jejuni and therefore represents an effective strategy for limiting infections with C. jejuni.