We reported experimental measurements of the viscosity and density of mixtures of 1,3-dimethylbenzene and carbon dioxide with mole fractions of carbon dioxide between 0 and 0.652. In this study, we used a vibrating wire viscometer–densimeter to measure the viscosity and density simultaneously at temperatures ranging from 298 to 423 K and at pressures up to 100 MPa. The Tait–Andrade and Tait equations have been used to correlate the experimental data for viscosity and density, respectively, at each composition, and the absolute average relative deviations (AARDs) were found to be ≤0.7% for viscosity and ≤0.1% for density. We also developed correlations for the viscosity and density surfaces as functions of temperature, pressure, and mole fraction with AARDs of 1.9% for viscosity and 0.3% for density. The data presented in this work will contribute to developing predictive models for the thermophysical properties of asymmetric mixtures under high temperature and pressure conditions.