Jane Nichols (Katherine Heigl) has been a bridesmaid for 27 weddings. One night when she is attending two weddings almost simultaneously, she meets Kevin Doyle (James Marsden), who helps her get home but discusses with her his cynical views of marriage. He finds her day planner in the cab they shared. Meanwhile, Jane's sister Tess (Malin Åkerman) arrives from Europe and falls in love with Jane's boss George (Edward Burns) at first sight. Tess pretends to like the same things that George does to get him to like her. Despite being in love with George herself, Jane does not reveal the truth and her sister's courtship progresses rapidly. Soon the new couple announce that they intend to marry in three weeks and Jane becomes the wedding planner.