Aim: The study was designed to compare the anesthetic efficacy of 2% mepivacaine with 1:100000 epinephrine to that of 4% articaine with 1:100000 epinephrine in inferior alveolar nerve block injection for mandibular molars with symptomatic irreversible pulpitis.Methods: 66 patients with symptomatic irreversible pulpitis in their mandibular molars were randomly allocated to two groups receiving IANB injection of either 2% mepivacaine with 1:100 000 epinephrine or 4% articaine with 1:100 000 epinephrine. Patients were asked to rate their pain level on a number rating scale (NRS) during access cavity preparation and root canal instrumentation. Patients who reported no or mild pain during the two procedures were considered successfully anesthetized, otherwise the case was considered anesthetic failure. Chi square test was used to compare the outcomes between the two groups.Results: anesthetic success of the mepivacaine group was (33.3%) while that of articaine was 45.5%. The difference between the two groups was not statistically significant (p= 0.31).Conclusion: Anesthetic efficacy of 2% mepivacaine was similar to that of 4% articaine in inferior alveolar nerve blocks for anesthetizing mandibular molars with symptomatic irreversible pulpitis.