Background and Aim: The study was planned to assess if chlorine dioxide (ClO2) mouthwash could be used as an alternative to chlorhexidine (CHX) mouthwash in cases of mild to moderate gingivitis. To compare the efficacy of CHX and ClO2 mouthwash in controlling plaque and gingivitis in mild to moderate cases. Materials and Methods: It was a randomized double blinded study conducted in 40 patients with mild to moderate gingivitis. After obtaining informed consent, subjects were randomly divided into two groups. The baseline values and after treatment values of plaque index (PI) and gingival index (GI) were recorded in both groups. Results of both thegroups were compared using unpaired t- test. P<0.05 was considered statistically significant. Statistical analysis and data management were performed using SPSS version 18 Results: A significant change in PI (0.00004) and GI (p value 0.00004) values was observed in subjects of chlorine dioxide (ClO2)group after 14 days. While no such significant change in GI (p value 0.58) and PI(p value 0.45)was observed in the subjects who received chlorhexidine (CHX)) mouthwash for 14 days. On intergroup comparison also no significant difference between the GI(p value) 0.417) and PI(p value 0.211) levels of CHX and ClO2 group were observed after 14 days. Conclusions: ClO2 was effective in suppressing the plaque and gingivitis in mild to moderate gingivitis. But on comparison its efficacy was similartoo CHX.