Liquid densities, p, of the ternary mixtures of water (1) + acetonitrile (2) + dimethyl sulfoxide (DMSO) (3) and their constituent binaries were measured at temperatures (293.15, 303.15, 313.15, 323.15, and 333.15) K and at ambient pressure (81.5 kPa) as a function of mole fraction. The excess molar volumes, V-m(E), partial excess molar volumes, V-i(E), and their values at infinite dilution, V-i(E,O), for binary and ternary liquid mixtures and thermal expansion coefficients, (x, of the pure component were calculated. The excess molar volumes are negative over the whole mole fraction range for binary mixtures of water (1) + acetonitrile (2) and water (1) + DMSO (3) and increase with increasing temperatures from (293.15 to 333.15) K. The excess molar volumes of acetonitrile (2) + DMSO (3) are negative and decrease with increasing temperatures from (293.15 to 333.15) K. The excess molar volumes are negative over the whole mole fraction range for the ternary mixture at all temperatures and decrease in the DMSO- and acetonitrile-rich region and increase in the water-rich region. The excess molar volumes were correlated with the Redlich-Kister equation and the Cibulka equation for the binary and ternary system, respectively. The excess molar volumes, V-m(E), were compared with values from the literature in the region of overlap.