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Rock wettability is a key parameter determining fluids distributions and migrations in hydrocarbon reservoirs. In shale rocks, the widespread existence of organic matter and the significant variation of total organic carbon (TOC) content lead to huge uncertainty on shale wettability. Therefore, this work systematically examines the dependence of shale wettability on TOC content (ranging from 1.2 wt% to 20.05 wt%). Multiple relations were probed experimentally, namely: 1) the effect of TOC content on n-dodecane (n-C 12) contact angles for shale-methane (CH 4)-n-C 12 systems at 5 MPa and 50 °C; 2) the effect of TOC content on n-C 12 contact angles for shale-carbon dioxide (CO 2)-n-C 12 systems at 5 MPa and 50 °C; 3) the effect of TOC content on brine contact angles for shale-brine-n-C 12 systems at 0.1 MPa and 50 °C; 4) the effect of pressure (0.1 MPa–25 MPa), temperature (25 °C and 50 °C) and TOC content on brine contact angles for shale-CH 4 -brine systems. The results demonstrate that for shale-CH 4 -n-C 12 , shale-CO 2 -n-C 12 and shale-brine-n-C 12 systems, the affinity of n-C 12 to shale increases with increasing TOC content. However, for shale-CH 4 -brine systems, the affinity of CH 4 to shale increases firstly, then flatten out and afterwards increases again; while shale wettability shifted from water-wet to CH 4 -wet with TOC content increase. In addition, a larger pressure renders shale less hydrophilic while a higher temperature causes shale more hydrophilic. The temperature influence is reduced with TOC content increase. The results can aid in better understanding of shale wettability at reservoir conditions. • Effect of TOC on shale wettability is systematically investigated. • Wettability shift from hydrophilic to hydrophobic with increasing TOC. • At reservoir condition (e.g., 20 MPa and 50 °C), a CH 4 -wet behaviour was found for 20.05 wt% TOC shale. [ABSTRACT FROM AUTHOR]