Wettability is a challenging property of oil and gas shale reservoirs, which are geologically and geochemically intricate formations. Furthermore, the mineral composition, organic matter content, generated pore types, pressure, temperature, and saturation conditions significantly affect the observed wetting affinity. Hence, a deep understanding of the complexities facing the researchers is needed. This review analyzes the most relevant published research on the wettability evaluation of shales for a better understanding and delineation. Here, the effects of shale composition, organic matter content, maturity, pore types, and reservoir conditions are addressed. It also focuses on the unconventional and emerging approaches to the wettability evaluation of shales. At last, future perspectives, concluding remarks, and recommendations are presented.