The development of efficient and environmentally sustainable membrane materials is essential for advancing water purification technologies. This review examines composite membranes that combine the properties of MXene and nanocellulose, focusing on their structural features, functional characteristics, and potential advantages in water treatment applications. Nanocellulose provides a biodegradable, renewable matrix with abundant surface functional groups, while MXene offers high hydrophilicity, electrical conductivity, and adsorption capacity. Based on a critical evaluation of published studies, the review outlines various fabrication strategies, discusses key factors affecting membrane performance—including morphology, surface modification, and interfacial interactions—and highlights the synergistic effects between the two components. The article systematizes current approaches to designing MXene/nanocellulose membranes and establishes a foundation for future scientific and technological development in this field.