Background:Bacteria are the main etiological factors in the development of dentinal caries and its progression to pulpal and periapical disease. Enterococcus faecalis is the bacterial species most frequently recovered from the root-filled teeth.Aim:This study aimed to evaluate the antimicrobial effectiveness of nanosilver (NS) solution as an endodontic irrigation solution of primary teeth against E. faecalis.Settings and Design:Thirty-six canals of primary teeth were selected for this ex vivo study.Methods and Materials:Thirty-six canals of primary teeth were prepared up to the file #35 and all of the specimens were sterilized. Then, root canals were inoculated with a suspension containing E. faecalis bacteria. The teeth were then randomly divided into three groups. Antimicrobial effectiveness was evaluated immediately after dividing into groups by counting colony-forming units on brain heart infusion broth plates.Statistical Analysis:Data were analyzed using Kolmogorov–Smirnov, Welch, and Dunnett's T3 tests.Results:Sodium hypochlorite showed the highest antimicrobial effectiveness against E. faecalis and showed significant differences compared with normal saline and NS solution (P < 0.001).Conclusion:Based on the results of this study, solution of NS particles can be used as an alternative to other root canal irrigating solutions.