This clinical trial aimed to compare pain scores and adverse events between buccal infiltration with 4 % articaine with epinephrine 1:200,000 and nerve block with 2 % lidocaine with epinephrine 1:100,000 in pulp treatment in mandibular primary molars. Twenty-six children received pulp treatments on both sides of the mandible with inferior alveolar nerve block with lidocaine and buccal infiltration with articaine in random sequences. Pain scores were assessed during injection and pulp removal by video observation and through participant’s self-reporting after the procedure. Additional local anesthesia and adverse events were monitored. The Wilcoxon Signed-Rank test and the McNemar test were used for statistical analysis. Pain scores during injection in lidocaine nerve block (2.4±1.2) and articaine infiltration (1.7±0.9) were significantly different (p=0.002). There was no statistical difference in pain scores during pulp removal, overall pain from self-reporting and additional local anesthesia. One case in each method reported lip biting after treatment. No other adverse events were reported in this study. In conclusion, mandibular infiltration with articaine was not different from inferior alveolar nerve block with lidocaine in pain control and adverse events when performing pulp treatment in mandibular primary molars; however, it provided less pain during injection.