Four teenage girls—Carmen, Tibby, Bridget, and Lena—are best friends from Bethesda, Maryland, who are about to separate for the summer for the first time in their lives. Lena is spending the summer in Santorini, Greece, with her grandparents; Tibby is staying at home; Bridget is going to soccer camp in Mexico; and Carmen is visiting her father in South Carolina. On one of their final days they go shopping together, the girls find a seemingly ordinary pair of jeans that fit them all perfectly and flatter their figures, despite their very different measurements. The girls dub them the Traveling Pants and decide to share them equally over the course of the summer. They part the next day, and the film focuses on each girl's journey separately.