After thermal poling, pyroelectricity and a pronounced dielectric hysteresis have been observed on films of a poly(vinyl alcohol) with azobenzene-alkoxy side chains (A2-PVA). Based on dielectric spectroscopy data and structural information from differential thermal analysis, the pyroelectricity can be explained with reversible dipole-density changes during thermal expansion, whereas the dielectric hysteresis is proposed to result from the polarisation caused by charge carriers, probably ions. These findings are also significant for the interpretation of dielectric hysteresis measurements on other polymer-electret materials.