Aim: This study was conducted to evaluate the post-operative pain following single versus multiple visits endodontic retreatment. Materials and Method: Fifty cases of single rooted teeth in (29) patients had failed endodontic treatment were selected according to inclusion criteria. Using simple randomization by table, the selected patients were divided into two groups, where Group I: the retreatment was performed in single visit. Group II; the retreatment was performed in two visits and Ca (OH) 2 mixed with 2% Chlorhxidin was used as intracanal medicament. The outcome of the retreatment was evaluated by recording post-operative pain and flare up. Results: There was no statistical significant difference in post-operative pain intensity between single and multiple visits endodontic retreatment after 24 hours as well as 7 days (P ≤ 0.05).The pain recorded was in mild category.