Aim: An experimental study was performed to evaluate the protective effects of probiotics on gut mucosa in peritonitis through antioxidant mechanisms. Methods: Thirty-two male Wistar albino rats were divided equally into four groups. The rats in Group 1 (control group) underwent laparotomy only. In group 2 (peritonitis group), peritonitis was induced in the rats by the cecal ligation and puncture (CLP) model. In group 3, the rats were treated with probiotics for five days after CLP-induced peritonitis. The last group of rats (group 4) were fed probiotics for five days before the CLP procedure and five days after the surgery. On the fifth day after surgery, all rats were killed, and tissue samples from the terminal ileum were obtained to evaluate the activities of myeloperoxidase (MPO), malondialdehyde (MDA), and glutathione (GSH). Histopathologic examinations were also performed to evaluate the grade of intestinal injury. Results: Myeloperoxidase and MDA activities were increased, GSH concentrations were decreased in group 2, compared with group 1. Intestinal MPO activities in group 4 were decreased compared with group 1 and group 2, indicating a reduction in oxidant activity. Malondialdehyde decreased in group 3 and decreased even more in group 4, compared with the peritonitis group (group 2). Glutathione concentrations were increased in group 4 compared with group 2 and group 3 (p<0.05). The Chiu scores of the probiotics groups, groups 3 and 4, were lower than those in group 2, indicating reduced mucosal damage in the probiotically fed groups. Conclusion: Probiotics have protective effects in peritonitis, which may be related to antioxidant mechanisms. This antioxidant effect of probiotics might occur when pre-conditioning with probiotics before peritonitis because there is sufficient time to prepare the tissues for oxidative damage.