Wettability in the methane (CH4)–liquid–rock system is a key parameter which determines gas recovery and geo-storage efficiencies. However, there is a lack of an overview over this area; thus, we critically review this parameter from experimental and theoretical perspectives and discuss the impact of pressure and temperature conditions, fluid properties (salinity, ion type, and aqueous versus nonaqueous) as well as rock surface chemistry and roughness. Current research gaps are identified, a future outlook is provided, and several conclusions are reached. Therefore, this mini review improves fundamental understanding of wettability in the CH4–liquid–rock system at in situ reservoir conditions and provides useful guidance on the areas of shale gas/coalbed methane recovery and natural gas geo-storage.