Embodiments of the disclosure are directed to cellular sheet pile retaining wall systems with unconnected tail walls, and associated methods of use and manufacture. In one embodiment, a retaining system includes a face wall having a plurality of interconnected face wall sheet piles. The individual face wall sheet piles have a first length and extend a first depth into soil, and the face wall sheet piles form an exterior surface facing an exterior environment. The system also includes a tail wall including a plurality of interconnected tail wall sheet piles extending from the face wall away from the exterior environment. The individual tail wall sheet piles have a second length greater than the first length, and the individual tail sheet wall piles extend a second depth into the soil that is greater than the first depth.