Caries management in the modern era has shifted away from the traditional surgical method toward a medical paradigm, which often includes fluoride therapy. Fluoride used in various forms has been proven to be effective in dental caries prevention. Silver diamine fluoride (SDF) and sodium fluoride (NaF) varnish are effective in arresting caries in primary molars. This study aimed to evaluate the effectiveness of 38% SDF and 5% NaF varnish in arresting caries in primary molars. This study was a split-mouth randomized controlled trial. The randomized controlled trial comprised 34 children aged 6-9 years with teeth having caries in both right and left primary molars without pulpal involvement. Teeth were randomly allocated into two groups. In Group 1 (n = 34), 38% SDF + potassium iodide was applied and in Group 2 (n = 34), 5% NaF varnish was applied. The second application was done after 6 months in both groups. Children were recalled at 6- and 12-month intervals and evaluated for caries arrest. Chi-square test was used to analyze the data. Caries arresting potential was found to be higher in the SDF group compared to the NaF varnish group at both 6-month (SDF - 82% and NaF varnish - 45%) and 12-month intervals (SDF - 77% and NaF varnish - 42%) and the difference was found to be statistically significant (P = 0.002 and 0.004, respectively). SDF was more effective in arresting dental caries in primary molars compared to 5% NaF varnish.