Cases have been reported of deformed geotextile-reinforced soil walls in cold regions. The deformation is likely to be caused by frost heavein the backfill soil of reinforced soil walls. To prevent the deformation caused by frost heave, the Hokkaido Regional Development Bureau of the Ministry of Land, Infrastructure, Transport and Tourism has established specific construction techniques. However, no preventive measures have been specified for geotextile-reinforced soil wallsalready in service. Toward proposing countermeasures to frost-heave deformation, full-scale tests were conducted. The results demonstrated that application of insulating materials to the outer surface of geotextile-reinforced soil walls helps to control frostheave deformation.