Deep localized‐state distribution in amorphous arsenic triselenide thin films has been measured with a modulated photocurrent technique. A peak in the deep localized‐state distribution is found at 0.79 eV above the valence‐band mobility edge. It is also found that the thermal emission rate of holes from the localized state at the peak is almost constant in the room‐temperature range but exhibits thermally activated behavior below and above the room‐temperature range. This anomalous temperature dependence of the thermal emission rate is interpreted on the basis of a thermally created defect.