Background/Objectives: Recent research indicate that probiotics positively influence oral health and impact oral micro-ecology. This study evaluates the effectiveness of pro-biotic mouthwash toward to Streptococcus mutans and Lactobacillus spp in oral cavity of patients with fixed orthodontic appliances comparing to conventional mouthwashes through count bacteria colonies and measurement of salivary pH. Methods: Collection of salivary and plaque samples from total 30 patients (15 males and 15 females), aged 14-21 years were done for colony counting of the caries related microorganisms and measurement of salivary ph. The study was included three groups with three treatment times as following: baseline, after two weeks, after one month, Group1: used Orthin Kin mouthwash, Group 2: Corsodyl mouthwash, Group 3: Probiotic mouthwash. Results: (33.3%, 96.6%) of samples were positive for S.mutans in male and female respectively while lactobacillus were (100%) in both .On the other hand, (93.33% ,3.33%) of plaque and saliva samples were positive for S.mutans respectively while , lactobacillus spp (100.0 %) of plaque and saliva samples. The treatment with probiotic, Orth Kin and Corsodyl mouthwashes were reduced S.mutans in plaque compared to baseline with sig-nificant difference at p< 0.05 between probiotic and both orthoKin and Corsodyl. While in saliva, treatment with probiotic showed increased lactobacillus spp level after month compared with baseline. However, the salivary PH showed there was no significant dif-ference between studied groups and baseline. Conclusion: Using the Probiotic mouth-wash for two weeks and a month gave effective results than others. However, the sali-vary pH did not change during the treatment in studied groups.