Aim: To clinically evaluate the effectiveness of 0.5% nano-chitosan mouth rinse on salivary pH and antimicrobial activity against salivary Streptococcus mutans (S. mutans) count and to ascertain its functionality as an anticaries mouth rinse in children. Materials and methods: A total of 42 participants with decayed, missing due to caries, and filled teeth (DMFT) index ≥4 and simplified oral hygiene index (OHI-S) score ≥1.3 in the age range of 7–12 years were recruited for the study after taking informed consent. Unstimulated saliva was collected, and baseline pH was calculated using pH strips. Children were asked to rinse 10 mL of nano-chitosan for 60 seconds once daily for about 10 days. The subjects were recalled for evaluation once the rinsing regimen was completed on the 11th day. The postrinse saliva sample was collected, and its pH was noted down. The bacterial count was determined by inoculating salivary samples on Mutans-Sanguis agar before and after mouth rinsing. Statistical analysis was done using a correlation test and paired t-test. Results: Statistically significant increase in salivary pH and a decrease in S. mutans count was observed after rinsing with nano-chitosan in comparison to baseline values. Conclusion: Nano-chitosan mouthwash was effective in altering the pH to a more desirable state and reducing the salivary S. mutans count. It may therefore be considered as a potential anticaries mouthwash. Clinical significance: Amidst the proliferation of numerous anti-Streptococcus preventive agents, there is much effort being put into developing safe, easily available, and natural alternatives to conventional mouth rinses. The introduction of a natural mouth rinse such as chitosan, which has lucrative properties, can be a valuable additive to the existing mechanical plaque control measures.