Objective: The objective of this study was to investigate the rise in temperature on the external root surface during 940 nm diode laser assisted root canal therapy. Materials and methods: A total of 120 human single rooted extracted teeth were included in the study. The root canals were enlarged and laser irradiation was performed at four different settings (1 W continuous mode, 1 W gated mode 10/10, 2 W continuous mode and 2 W gated mode 10/10). The rise in temperature was measured at apical, middle and cervical thirds. The temperature changes were evaluated by a thermocouple. The threshold temperature rise of 7°C is commonly considered as the highest temperature limit biologically acceptable to avoid periodontal damage. Results: The mean temperature rise on external root surface in our study was below 7°C in all parameters and all portions of root surface. Conclusion: The 940 nm diode laser at 1 W CM, 1 W gated 10/10, 2 W CM and 2 W gated 10/10 can be considered safe for use for laser assisted root canal therapy.