Light scattering and viscosity measurements were carried out for thermally renatured xanthan samples with various molar masses and molar mass distributions. The increases in the molar mass, radius of gyration, and intrinsic viscosity of a xanthan sample with high molar mass and wide molar mass distribution upon renaturation were smaller than in xanthan samples with lower molar masses and narrower molar mass distributions. This behavior could be explained by the increase in “intra-dimer-renaturation” caused by the slower diffusion of xanthan with higher molar mass.