The presence of a thin amorphous intermixed layer at the platinum‐GaAs interface in as‐deposited Pt/GaAs and Si/Pt/GaAs samples has been investigated via high‐resolution electron microscopy, microdiffraction, and energy dispersive spectroscopy. The intermixed layer forms below the native oxide of the GaAs substrate and consists of three elements, platinum, gallium, and arsenic. We suggest that this layer forms during the deposition process of the platinum.