Early lifeCavallari was born January 5, 1987 in Denver, Colorado, the second of three children of Judith Spies (née Eifrig) and Dennis Cavallari. When her mother divorced her father, her older brother Mike moved with their father to Laguna Beach, California, while she moved with her mother to the village of Barrington, Illinois, a suburb an hour northwest of Chicago. After difficulties adjusting to a new life with a stepfather and stepbrother, Kristin moved to California to live with her father. Instead Kristin was enrolled at Santa Margarita Catholic High School for her freshman year. After she attended a Driver's Education course through Laguna Beach High School, her father enrolled her in LBHS.
2006-2010: Laguna Beach and The Hills
Cavallari was in her junior year of high school when the first season of Laguna Beach: The Real Orange County began production. At the time, she was involved in an on-and-off relationship with senior Stephen Colletti. Cavallari's romance with Colletti caused a rivalry with another cast member, Lauren Conrad. The love triangle became one of the series' central plotline. 
In May 2009, Cavallari confirmed that she would be joining the cast of the popular MTV reality series The Hills. She appeared in the mid-season finale that aired on May 31, 2009 and appeared as a regular in the remainder of the fifth season. She inked a deal with MTV to appear as a series regular throughout two more seasons of the series following the fifth. The sixth and final season aired summer 2010.
2006-2009: Acting endeavorsAfter her stint on Laguna Beach, Cavallari headed to Los Angeles and briefly enrolled at University of Southern California. She signed on the UPN reality television series Get This Party Started, which premiered February 7, 2006. The series was canceled after airing two episodes due to extremely low ratings. She guest starred in another UPN series Veronica Mars in one episode. She has appeared in numerous television roles such as CSI: NY, Cane and Adventures in Hollyhood.
In 2006, she signed on as Crystal in the horror film Fingerprints. Filming took place throughout April and May 2006 in two Oklahoma towns. The film premiered at Screamfest on October 16, 2006. The film won Best Feature at the 2006 New York City Horror Film Festival. The film was released in 2007 to mixed to positive reviews. She also played a small role in "Wristcutters: A Love Story," an independent film, directed by Goran Dukic in 2006.
In 2008, she had a supporting role in Spring Breakdown alongside Amy Poehler as Summer. The film was released straight-to-DVD on June 2, 2009 and received mixed reviews. She also starred in the independent film Green Flash alongside Torrey DeVitto.
In 2009, she starred in the independent American high school comedy film Wild Cherry as Trish, which also starred Rumer Willis. She also starred in the straight-to-DVD film National Lampoon's Van Wilder: Freshman Year as Kaitlyn. The film was released July 14, 2009 to mixed to negative reviews.
PhilanthropyCavallari has been involved in the "Until There's a Cure" public service advertising campaign to raise awareness and funds for AIDS and HIV research and vaccine development. In 2006, Cavallari appeared in ads for PETA, and has also appeared as a celebrity spokesperson for "We Are Ellis Island", a campaign for the restoration of historic buildings on Ellis Island. In February 2009, she posed for the NOH8 Campaign in support of gay marriage.
Cavallari is currently engaged to Chicago Bears quarterback Jay Cutler.
|2004 to 2005||Laguna Beach: The Real Orange County||Herself||28 episodes|
|2006||Get This Party Started||Host||2 episodes|
|2006||Veronica Mars||Kylie Marker||1 episode|
|2007||Cheerleader Camp||Julie||Television movie|
|2007||Cane||Casey||Episode: "Family Business"|
|2008||Green Flash||Lana||Direct-to-DVD release|
|2008||CSI: NY||Isabelle Vaughn||Episode: "Forbidden Fruit"|
|2008||Spring Breakdown||Seven #3|
|2009||Wild Cherry||Trish Van Doren|
|2009||National Lampoon's Van Wilder: Freshman Year||Kaitlin Hays||Direct-to-DVD release|
|2009 to 2010||The Hills||Herself||23 episodes|
|2011||The Middle||Ms. Devereaux||Episode: "Friends, Lies, and Videotape"|