An article of footwear may have an upper and a sole structure secured to the upper. The sole structure includes a fluid-filled chamber with a first surface, an opposite second surface, and a third surface extending between the first and second surfaces. Whereas the first surface and the second surface each have a thickness of one sheet of a polymer material, the third surface may be formed to have a thickness of two overlapping sheets of the polymer material. The third surface may be exposed to an exterior of the footwear to form a portion of a side surface of the sole structure.