The reversal process of the free layer of two spin valves (SVs) with crossed anisotropy was studied as a function of temperature by transmission electron microscopy. In situ magnetizing experiments were carried out using the Fresnel imaging mode at room temperature, 100 °C, and 200 °C. The two SVs studied had slightly different synthetic antiferromagnetic (SAF) structures, the magnetic layers being thicker in one than the other. It was found that the SV with the thinner SAF layer was less thermally stable. Moreover, a change in the reversal process was observed at elevated temperature while no changes were seen for the SV with thicker SAF. Insight into why the reversal mode varied in the way it did was obtained using a modified Stoner–Wohlfarth model.