Purpose: The accuracy of the automated external defibrillator (AED) is susceptible to environmental factors such as vibration, motion artifacts, and electromagnetic interference (EMI). The purpose of this study was to evaluate whether the EMI produced by an electric mattress can affect the performance of AEDs. Methods: Four commercially available AEDs were evaluated under four ECG rhythm settings (normal sinus rhythm, asystole, ventricular fibrillation, and ventricular tachycardia) with or without an electric mattress. The sensitivity, specificity, positive predictable value, negative predictable value, and accuracy of AEDs were calculated to differentiate shockable from nonshockable rhythms. Times required to interpret the ECGs were checked with and without an electric mattress. Results: A total of 320 tests were recorded, and each AED was tested a total of 80 times. Depending on the AED model used on an electric mattress, sensitivity ranged from 55% to 90% with a specificity of 100%, and accuracy ranged from 77.5% to 95%. For some AEDs, sensitivity was reduced compared to the control. Although there was no significant difference in times required to interpret ECG signals with or without an electric mattress, some AEDs detected a relatively small interference as motion artifacts when an electric mattress was used. All recorded ECG rhythms on an electric mattress showed baseline artifacts and these artifacts lessened with increasing distance from an electric mattress. Conclusion: This study suggests that an electric mattress could affect the shockable rhythm performance of some AEDs. Electromagnetic interference generated by an electric mattress could interfere with the ability of some commercial AEDs to correctly interpret stimulated ECG rhythms and provide appropriate defibrillation.