In this work, an equation of state (EoS) is developed to predict accurately the phase behavior of ionic liquid + CO2 systems based on the truncated perturbed chain polar statistical associating fluid theory (tPC-PSAFT) EoS. This EoS accounts explicitly for the dipolar interactions between ionic liquid molecules, the quadrupolar interactions between CO2 molecules, and the Lewis acid-base type of association between the ionic liquid and the CO2 molecules. Physically meaningful model pure-component parameters for ionic liquids are estimated based on literature data. All experimental vapor-liquid equilibrium data are correlated with a single linearly temperature-dependent binary interaction parameter. The ability of the model to describe accurately carbon dioxide solubility in various 1-alkyl-3-methylimidazolium-based ionic liquids with different alkyl chain lengths and different anions at pressures from 0 to 100 MPa and carbon dioxide fractions from 0 to 75 mol % is demonstrated. In all cases, good agreement with experimental data is obtained.