Objective: Remote cardiac implantable electronic device (CIED) interrogators, originally developed for home use, have been proven to be efficacious in clinical settings, especially emergency departments. Concern exists that attempting to interrogate a CIED with the remote interrogator of a different brand, i.e., a brand-mismatched interrogator, may cause device malfunction. The aim of this study was to determine if intentionally attempting to interrogate a CIED with a brand-mismatched remote interrogator resulted in device malfunction. Methods: A total of 75 ex vivo CIEDs manufactured by various companies underwent attempted interrogation by a brand-mismatched remote interrogator. CIED settings were compared before and after attempted mismatch interrogation. A total of 30 in vivo CIEDs were then randomized for an attempted 2-minute mismatched remote interrogation by one of the two possible mismatched remote interrogators. CIED settings were compared before and after attempted mismatch interrogation. Results: Of 150 ex vivo brand-mismatched interrogations, no device setting changes or malfunctions occurred; no remote interrogators connected to a mismatched CIED, and no devices were turned off. In the 30 patients undergoing brand-mismatched interrogations, the mean (standard deviation) age was 71.6 ( ± 14.7) years, 16 (53%) were male, with 24 pacemakers (80%), four pacemaker/implantable cardioverter defibrillators (13%), and two implantable cardioverter defibrillators (7%). Of the 30 mismatched interrogations performed, no device setting changes or malfunctions occurred; no remote interrogators connected to a mismatched CIED, and no devices turned off. Conclusion In a total 180 attempted brand-mismatched CIED interrogations, no CIED malfunctions occurred. This suggests that the use of remote CIED interrogators when device manufacturer is unknown is unlikely to result in adverse CIED-related events.