Background: Cow's milk protein allergy (CMPA) is the most common food allergy in infants. The current standard of care (SOC) involves eliminating the allergen from both the infant's and mother's diet for 2-4 weeks. The purpose of this study is to assess the effectiveness of Lactobacillus rhamnosus (Ramnoflor) in reducing the duration of bleeding in these infants. Methods: This randomized clinical trial was conducted at Bahrami Children's Hospital on breastfed infants who were diagnosed with CMPA and had a positive occult blood (OB) test. Patients were randomly assigned to either the control or case groups. All patients received SOC therapy, with the case group receiving Ramnoflor and the control group receiving a placebo. Data were recorded on the checklist, and the children were followed and visited three times during the study, with an OB assessment at each visit. Results: The study enrolled 48 infants. Among the infants in the case group, the OB test was positive in four cases (8.3%) on the fifth day. However, there were no positive cases on the 14th and 30th days. The prevalence of this test was significantly lower in patients who received probiotics compared to the control group on the fifth day (p < 0.001). There were no positive OB tests on the 14th and 30th days in any of the groups, and no significant difference was observed between the groups. Conclusion: The addition of L. rhamnosus to SOC therapy led to a decrease in the duration of rectal bleeding in infants with CMPA compared to the control group.