CO2 and CH4 wettabilities of organic-rich shale are important physicochemical parameters that significantly influence CO2 sequestration and CH4 production. However, there is a serious lack of understanding of these aspects because the data available are scarce. Thus, we evaluated organic-rich shale CO2 and CH4 wettabilities (i.e., brine/shale/gas systems) through advancing and receding brine contact angle measurements as a function of pressure, temperature, salinity, and ion type (as these can vary significantly in underground formations). The results indicated that the brine contact angles for both CO2/CH4-brine-shale systems increased with pressure and salinity, but decreased with temperature. However, these effects were much less significant for CH4. Furthermore, the brine contact angles for the CO2-brine-shale system reached 180 (i.e., the shale was completely wetted by CO2) when the pressure reached 30 MPa at 343 K and-9 MPa at 298 K. The brine contact angles for the analogue CH4 systems was much lower (50-90), only indicating weakly water-wet to intermediate-wet conditions. Finally, the brine contact angles for CO2-brine-shale system were also larger for divalent ions (Ca2+, Mg2+) than for monovalent ions (Na+, K+), while ion type had no significant influence on CH4 wettability. However, a similar CO2/CH4 density resulted in a similar wettability. Consequently CH4 could not be used as a proxy for predicting CO2 storage capacities, unless they have similar densities.