McCullah was born in the Philippines, where her father had been assigned with the United States Navy performing counterespionage duties. She grew up in Bergen County, New Jersey, and graduated from Indian Hills High School in her hometown of Oakland, New Jersey. As a high school student, she maintained in her diary 10 Things I Hate About Anthony, her boyfriend at the time, which ultimately led to the title of her 1999 film, 10 Things I Hate About You.
She is a graduate of James Madison University in Virginia where she was a member of Alpha Gamma Delta sorority. She wrote most of the published screenplays with her screenwriting partner Kirsten Smith. In 2005 she also wrote her first novel The Bachelorette Party.
- The Bachelorette Party (2006) - ISBN 978-0-312-32621-0
- 10 Things I Hate About You (1999) - an adaptation of William Shakespeare's The Taming of the Shrew set in a modern American high school
- Legally Blonde (2001) - screen adaptation of Amanda Brown's novel Legally Blonde
- Ella Enchanted (2004) - screen adaptation of Gail Carson Levine's 1997 novel Ella Enchanted
- She's the Man (2006) - an adaptation of William Shakespeare's play Twelfth Night, or What You Will.
- The House Bunny (2008)
- The Ugly Truth (2009)
- Crazy Kind of Love" (2013)
- a screenplay of her novel The Bachelorette Party.
- Longsdorf, Amy. "N.J. writer puts her mark on Hollywood", The Record (Bergen County), July 20, 2009. Accessed August 4, 2011. "Screenwriter and former Oakland resident Karen McCullah Lutz is the first to admit she owes New Jersey a big debt of gratitude. Spending four years at Indian Hills High School sparked her love of Springsteen and the Paramus Park Mall, but Lutz is particularly grateful for an even more lasting Garden State gift."
- Beckerman, Jim. "This blonde is having more fun as a screenwriter", The Record (Bergen County), September 7, 2008, p. F-8. Accessed September 7, 2008.
- "Montpelier - James Madison University Magazine". Jmu.edu. 1999-03-31. Retrieved 2014-03-07.