The warm-water extraction of mined oil sands recovers the bitumen content as a froth, with significant amounts of emulsified water and fine mineral solids. Direct thermal processing of this bitumen water mixture, giving hydrothermal conditions, could reduce the number of process steps. In this study, the mineralogy and wettability of fine solids in Athabasca bitumen froth before and after hydrothermal treatment at 392 degrees C for 30 min at 15 MPa were investigated. The clay minerals, mainly kaolinite and illite, were unchanged, but siderite (FeCO3) and pyrite (FeS2) were converted to pyrrhotite (Fe(1-x)S) after the treatment. This conversion can be advantageous during direct hydrothermal treatment of bitumen froth because it fixes organic sulfur. The initial fine solids in the bitumen froth possessed a wide range of wettability, but they turned uniformly more oil-wet after the hydrothermal treatment. Consequently, the fine solids mostly stayed in the oil phase after the hydrothermal treatment and did not act as stabilizers for water-in-oil emulsions. The filterability of the fine solids in the bitumen froth was also significantly increased. Consequently, hydrothermal treatment of Athabasca bitumen froth could be used to destabilize water-in oil emulsions and facilitate fine solids removal by filtration.