Purpose: This study evaluated the effectiveness of using EndoVac irrigation device on microbial reduction and postoperative pain in single rooted teeth with necrotic teeth and apical periodontitis after single visit treatment. Subjects and Methods: Thirty six single rooted teeth from patients of age range between 20 and 50 years old were involved in this study. According to irrigation procedures, patients were assigned randomly and equally into two groups of 18 teeth per group. Group I (conventional irrigation) and Group II (EndoVac irrigation). Irrigating solution for both groups was 2.5% sodium hypochlorite. All patients were treated in a single visit. The access cavity was prepared, and a microbiological sample (S1) was obtained. The root canal was chemomechanically prepared with ProTaper rotary instruments up to #F4. Finally, after irrigation activation, the second microbiological sample (S2) was collected. Samples were cultured on plates of nutrient agar, incubated for one day at thirty seven °C, and colony forming units (CFU) were counted and recorded. The primary outcome assessed microbial reduction in both groups. The pain was measured using a Numeric rating Scale (NRS) at 6, 12, 24, and 72 hours to determine the secondary outcome. Results: The mean percentage reduction in microbial count in Group II was statistically significantly higher than in Group I (P ≤ 0.05). Conventional group (G I) showed statistically significantly higher pain scores than EndoVac group (G II) (P ≤ 0.05). Conclusion: In necrotic teeth with apical periodontitis, EndoVac could be utilized as an adjunct to conventional root canal irrigation.