The cooperative molecular reorientation in methacrylate copolymer films with hexamethylene spacer groups terminated with photoreactive hydrogen (H) bonded 4-oxycinnamic acid (CA) and photoinactive 4-oxy-4′-methoxybiphenyl (MB) in their side chains was investigated by irradiating with linearly polarized ultraviolet light (LPUV) and subsequent annealing. A thermally enhanced cooperative in-plane orientation of both CA and MB side groups perpendicular to the polarization (E) of LPUV light was obtained when the annealing temperature was in the liquid crystalline temperature range of both mesogenic side group. On the other hand, thermal enhancement of the in-plane molecular reorientation did not occur when the annealing temperature was out of the LC temperature range of the MB. It was clarified that the amount of axis-selectively photoreacted H-bonded CA groups and the LC mesomorphism of the copolymer film play an important role in the thermally enhanced cooperative molecular reorientation.