Abstract: Mild thermal treatment is an important partial upgrading technique to enable bitumen pipeline transportation, but no attention has been paid to the impact of mild thermal treatment on the emulsification behavior of emerging partially upgraded bitumen. Asphaltene compounds are active emulsion stabilizers in bitumen oil. The emulsion stabilizing capacity of bitumen asphaltenes was investigated, before and after a mild thermal treatment at 400 °C. The structural morphology and mechanical property of the asphaltene interfacial films were analyzed by using a combination of cryo-SEM, Langmuir trough, and Brewster angle microscopy. The thermal treatment significantly enhanced the emulsion stabilizing capacity of bitumen asphaltenes; the interfacial films formed by the thermally treated asphaltene samples appeared to be rougher and thicker with more abundant micron-scale wrinkle structures. The interfacial corrugation may intensify the mechanical stability/flexibility of the asphaltene films and consequently strengthen the stability of emulsion droplet.