With the advent of high-intensity short pulse lasers it has become possible to achieve extremely high intensities. When such laser pulses interact with plasmas or high-energy electron beams, radiation damping, which is usually small, can become large. We examine the effects of radiation damping on the backscattered Thomson radiation numerically and analytically. Using parameters comparable to the laser and microtron at the Advanced Photon Research Center we find that the overall spectrum is down-shifted and that the overall amplitude of the radiation is smaller than in the case with no damping.