In 2003, Hahn appeared in a supporting role alongside Kate Hudson and Matthew McConaughey in the romantic comedy film "How to Lose a Guy in 10 Days." The following year she appeared in "Win a Date with Tad Hamilton!", ', "Around the Bend", and "." She later had more supporting roles in films, including the 2005 romantic comedy-drama "A Lot like Love" starring Ashton Kutcher and Amanda Peet; "The Holiday" (2006) with Cameron Diaz; the science fiction adventure drama "The Last Mimzy" (2007) alongside Rainn Wilson; "Step Brothers" (2008); "Revolutionary Road" (2008) starring Leonardo DiCaprio and Kate Winslet; and ' (2009), "How Do You Know" (2010), "Our Idiot Brother" (2011), and "Wanderlust" (2012).