Objective: The objective of this study was to assess and compare the effect of calcium hydroxide/ nano silver particulate combination intracanal medicament versus calcium hydroxide intracanal medicament on postoperative pain in symptomatic root canal treatment failure cases.Subject and Methods: Forty patients with symptomatic root canal treatment failure in anterior and premolar teeth were included. After through clinical and radiographic diagnosis, patients were enrolled into two equal random group each of 20 patients. Previous coronal restoration was removed along with gutta percha using nickel titanium rotary retreatment files, Standard endodontic treatment was performed in two visits using rotary nickel titanium files for shaping, 2.5% sodium hypochlorite for cleaning. Using Lentulo Spiral Filler, medicaments were placed under aseptic conditions into the canals according to each group at the end of the first visit, lateral condensation technique with resin sealer for obturation was done 7 days later. Pain was assessed pre-operatively, then after 6, 12, 24 and 48 hours after root canals obturation. Numerical Rating Scale (NRS) was used as the primary outcome measure. Patients were given analgesics to be administrated in case of emergency. All demographic data and NRS scores were collected from the patients and statistically analyzed.Results: Results showed that nano silver solution mixed with calcium hydroxide significantly reduced the incidence of postoperative pain after 6 hrs. There was a statistically significant decrease in median NRS scores preoperatively compared with all other post-operative time follow up periods. There was no significant difference in incidence of analgesic intake between the two groups.Conclusions: Nano silver seems to have a good potential to be used as an appropriate vehicle of Ca (OH) 2 in order to reduce the incidence of post-operative pain in the first 6 hours following root canal retreatment.