An article of footwear may include an upper and a sole structure secured to the upper. The upper includes at least one illuminable strand located to be visible from an exterior of the article of footwear. In some configurations, the upper includes a power source at least partially embedded within the upper and electrically-coupled to the illuminable strand. In another configuration, the upper includes a foundation layer and a cover layer that are secured to each other, and the illuminable strand is located between the foundation layer and the cover layer.