Background: To compare the action of intracanal medicaments: Calcium hydroxide and 2% Chlorhexidine, 10% Metronidazole gel, Septilin and 2% Chitosan as intracanal medicaments after instrumentation with One curve® (Micromega) Rotary Single-file System at 6 hrs, 12 hrs, 24 hrs, 48 hrs, 72 hrs and one week. Method: Total of 50 mandibular molars were included (n=50) with occlusal caries and mild to moderate pre-operative pain with minimal periapical radiolucency. After completing access cavity preparation under local anaesthesia and isolation with rubber dam, instrumentation with One curve single file was completed and patients divided into groups of medicaments with a group of no medicaments or only normal saline. The data was statistically analysed using Friedman’s two way analysis, Kruskal Wallis ANOVA and Post hoc pairwise comparison. Results: In all the study groups, there was significant decrease in post-operative pain at 6 hrs. Calcium hydroxide with 2% Chlorhexidine showed significant decrease in post-operative pain and its efficacy was evident from 24 hrs upto 7 days. Metronidazole 10% intracanal medicament at 6 hrs and 12 hrs showed maximum pain reduction post-operatively, which had sustained effect upto 7 days. Conclusion: In accordance to the results, it could be concluded that 10% Metronidazole and Calcium hydroxide plus 2% Chlorhexidine proved to be beneficial for reducing post-operative pain followed by Septilin; Septilin and 2% Chitosan showed shorter duration of efficacy as compared to other medicaments.