Abstract We analyze the dust properties of 57 870 μ m-selected dusty star-forming galaxies in GOODS-S using new deep Atacama Large Millimeter/Submillimeter Array 1.2, 2, and 3 mm continuum imaging together with other far-infrared through millimeter data. We fit the spectral energy distributions (SEDs) with optically thin modified blackbodies to constrain the emissivity indices and effective dust temperatures, finding a median emissivity index of β = 1.78 − 0.25 + 0.43 and a median temperature of T d = 33.6 − 5.4 + 12.1 K. We observe a negative correlation between β and T d . By testing several SED models, we determine that the derived emissivity indices can be influenced by opacity assumptions. Our temperature measurements are consistent with no evolution in dust temperature with redshift.