The effect of pressure on the volume of liquid 1,2-dichloro-1,2,2-trifluoroethane (R123a) has been measured relative to the volume at 0.1 MPa with a bellows volumometer for pressures up to 380 MPa over the temperature range (278.15 to 298.14) K and up to about 275 MPa for (313.14 to 338.13) K. The experimental volume ratios have been represented by equations to enable interpolation and extrapolation of volumetric properties. Isothermal compressibilities, isobaric expansivities, internal pressures, and the change in isobaric heat capacity from its value at 0.1 MPa have been calculated. Although there are similarities between these properties and those of 2,2-dichloro-1,1,1-trifluoroethane (R123), there are differences, indicating the effects of the greater asymmetry of the molecular structure of R123a.