Densities for solutions of [C(n)mim]Br (n = 4, 8, 10, 12) ionic liquids (ILs) in dimethyl sulfoxide (DMSO) have been determined as a function of ionic liquid concentration at the temperature T = (293.15, 298.15, 303.15, 308.15, and 313.5) K and atmospheric pressure. The apparent molar volumes, apparent molar volumes at infinite dilution, and limiting apparent molar expansivities of the ILs have been obtained from the experimental density data. These data were used to understand the effect of the alkyl chain length of the ILs and experimental temperature on the IL-DMSO interactions occurring in the studied solutions. It was shown that the apparent molar volumes at infinite dilution increased with increasing alkyl chain length of the Its and temperature of the systems. Furthermore, the values of the limiting apparent molar expansibilities were found to be positive and decrease with increasing temperature.