This clinical study evaluated postoperative pain intensity following primary root canal treatment using radiographic method and electronic method for working length determination in a single session approach. Methods: Seventy-eight asymptomatic patients with molars indicated for primary non-surgical root canal treatment were assigned into two groups according to the method of working length determination. Preparatory phase was performed through hybridization in both the preparation technique and irrigation protocol. Obturation was performed using cold lateral compaction technique. The primary outcome was that postoperative pain was recorded using a verbal rating scale (VRS) with well-defined categories at 5-time intervals after root canal treatment by: 4, 6, 12, 24 and 48 hours. The secondary outcome was analgesics intake. Data was analyzed using the Mann-Whitney U, Fisher's exact, Friedman's test, Dunn's test, Chi-square tests, and Student's t-test (P ≤ 0.05). Results: After 4 hours, the radiographic group showed a statistically significant higher pain score than the electronic group (P-value <0.001). After 6 hours, radiographic group showed a statistically significant lower pain score (P-value = 0.012). After 12 hours, radiographic group showed a statistically significant higher pain score than (P-value <0.001). After 24 and 48 hours, there was no statistically significant difference between the two groups. The radiographic group showed a statistically significant higher percentage intake of analgesics. Conclusions: Both postoperative pain and analgesic intake were influenced by the method of working length determination. In addition to reduced exposure to radiation, the electronic method was found to be a non-pharmacological method for avoiding postoperative pain.