A flexible substrate structure including a flexible substrate, a first dielectric layer, a metal-containing layer and a second dielectric layer is provided. The first dielectric layer is located on the flexible substrate. The metal-containing layer has a reflectivity greater than 15% and a heat transfer coefficient greater than 2 W/m-K. The metal-containing layer is disposed between the first dielectric layer and the second dielectric layer, and the second dielectric layer is an inorganic material layer. A flexible transistor including the above-mentioned flexible substrate structure and a method for fabricating the same are also provided.