The 1-octanol/water partition coefficients (log P) at 298.15 K and the vapor-liquid and liquid-liquid equilibria (VLE and LLE) of biofuel-related mixtures have been predicted with four different thermodynamic models: conduct-like screening models for real solvent (COSMO-RS), conduct-like screening models for segment activity coefficient (COSMO-SAC) (2002 version), modified COSMO-SAC (2006 version), and universal functional activity coefficient (UNIFAC). The 2002 version of COSMO-SAC gives more reasonable predictions for log P for most investigated mixtures than the other two approaches when appropriate molecular geometries are chosen for the computation of the sigma profiles. However, the COSMO-RS model gives better predictions for VLE pressures and vapor-phase compositions for biofuel-related mixtures, as well as for the LLE of the 1-octanol + water and furfural + water mixtures. The accuracy of the models for the predictions of the partition coefficients and VLE may be improved by changing the molecular conformations used to generate the sigma profiles. Generally, the three COSMO-based models give better predictions than UNIFAC for log P and VLE of the investigated systems and can be applied to predict the thermodynamic properties of the biofuel-related mixtures especially when no experimental data are available.