Objectives: To determine the effect of electromagnetic radiations (emitted by Xiaomi Redmi Note 9 Pro Device) on working length determination of 3rd generation Electronic Apex Locator (RootZx).
 Materials and Methods: Twenty nine intact, non-carious, single-rooted teeth were decoronated at the cementoenamel junction. Visually, working length was determined by using a#15 K-file and it was taken as standard length. The effect of cellular phones on electronic working length (EWL) was determined under 2 experimental settings: (1) in a closed room with poor signal strength and (2) in a polyclinic set up with good signal strength and 2 conditions: (a) electronically with cellular phone in standby mode (b) electronically, with mobile phone in physical contact with EAL and in calling mode for a period of 25 seconds. The EWL was measured 3 times per tooth under each condition. Stability of the readings was scored. The data was analyzed by using Microsoft Excel.
 Results: The EWL measurements were not influenced by the presence of cellular phone and could be determined under all experimental conditions. 
 Conclusion: Within the limitations of this study, it can be concluded that mobile phones do not interfere with the EWL determination. Keyword: working length, apex locator, root canal, endodontics