The thermal diffusivities of 2-methoxy-2-methylpropane (MTBE, mass purity, > 0.990, GC) were measured by using the dynamic light scattering method at T = (303.15 to 493.15) K and p = (1.5 to 10) MPa, including saturated liquid, saturated vapor, and compressed liquid. The expanded relative uncertainty in thermal diffusivity was estimated to be less than 2.0 % over the entire investigated range. The polynomial representation for thermal diffusivity of MTBE was proposed by employing the experimental results. Comparing the calculated results with the experimental data, the average absolute deviations are 0.59 % for saturated liquid, 0.38 % for saturated vapor, and 0.43 % for compressed liquid.