Flexible spin valves were fabricated with single-crystalline two-dimensional (2D) MX2 (M = Mo, W; X = S, Se) monolayers as spacer layer. Ferromagnetic metals were used as top and bottom layers in the flexible spin valve devices. The spin valve effects are studied at room- and variable -temperatures. The temperature dependence tunneling magnetoresistance of the spin valves is studied and analyzed. This research paves the way for possible flexible spin valves composed of all 2D layers (2D ferromagnetic layers and spacer layer) in the future towards ultra- thin and small memory devices in flexible electronics.