The sharp temperature changes in nature (e.g., forest fires, ice, and snow) can cause mechanical damage to trees and bamboo. The mechanical properties of Mongolia Scotch pine (Pinus sylvestris L. var. mongolica) and Moso bamboo (Phyllostachys edulis) were investigated by a three-point bending test with a repeated thermal shock process (i.e., sudden changes of temperature). The experimental results indicated that the flexural modulus, flexural strength, and deformation work per volume decreased almost linearly with the increased repetition of thermal shock treatment for both Mongolia Scotch pine and Moso bamboo. The damage caused by repeated thermal shock was stronger for Mongolia Scotch pine, as compared to Moso bamboo, under the same thermal shock treatment. Thus, the experimental results provided basic data for engineering applications of Mongolia Scotch pine and Moso bamboo after natural disturbances.