Recently, MXene, a novel two-dimensional (2D) material, shows promising potential in many fields. Among these fields, gas separation and adsorption have emerged as new application areas for MXene. The number of studies relevant to the application of MXene in gas separation and adsorption is gradually increasing, making it a hot spot in scientific research. Therefore, timely and systematic reviews of the strengths and weaknesses of MXene are crucial to its further development. This article focused on the application of MXene in gas separation and adsorption. In this review paper, we presented some preparation methods of large MXene layers and practicable strategies for utilizing them to enhance the operational stability of MXene membranes, and the latest research advancements in the application of MXene in gas separation and adsorption. In terms of gas separation, we provided a systematic summary of the research progress based on the techniques used to prepare MXene membranes. As for gas adsorption, we discussed the research progress from both experimental and theoretical perspectives. This discussion was divided into three parts: (1) exploration of the impact of the surface groups on gas adsorption process; (2) analysis on the effect of gas adsorption in gas sensing; and (3) study on theoretical calculation pertaining to gas adsorption and separation. Finally, we evaluated the advantages and disadvantages of using MXene in gas separation and adsorption and then outlined the potential avenues for the future development of MXene. It is expected that this review may provide valuable insights and guidance for the researchers engaged in promoting the intensive study and the broad application of MXene.