The research on heteroaromatic azoswitches has been blossoming in recent years due to their astonishingly broad range of properties. Minimal chemical modifications can drastically change the demeanor of these switches, regarding photophysical and (photo)chemical properties, promoting them as ideal scaffolds for a vast variety of applications based on bistable light-addressable systems. However, most of the characteristics exhibited by heteroaryl azoswitches were found empirically, and only a few works focus on their rationalization. Herein we report on a mechanistic study employing phenylazoindoles as a model reference, combining spectroscopic experiments with comprehensive computational analysis. This approach will elucidate the intrinsic correlations between the molecular structure of the switch and its thermal behavior, allowing a more rational design transferable to various heteroaryl azoswitches.