We report here an unprecedented utility of redox-active transition-metal complexes as heat-shielding materials. A poly(vinyl alcohol) film containing mixed-valent cluster [Ru3-(mu(3)-O)(mu-CH3CO2)(6)(mbpy(+))(3)](PF6)(3) (1) (mbpy(+) = 1-methyl-4,4'-bipyridinium cation), which strongly absorbs light in the near-infrared region, shows heat-shielding characteristics whose efficiency is found to highly depend on the redox state of the cluster dye.