Marquardt was born in Tillamook, Oregon after her family moved there from Lodi, California. Shortly after her birth, Marquardt's mother moved the family back to California, where Marquardt was raised. Her parents eventually divorced and later her mother remarried. Marquardt lived with her mother and siblings at their stepfather's ranch. Marquardt attended Galt High School for her freshman and sophomore years and then transferred to Lodi High School from which she graduated in 1990.

Some of her male friends thought that she should pose for Playboy magazine. Marquardt sent a letter to Playboy inquiring how to become a Playmate. Then, Marquardt enrolled at San Joaquin Delta Junior College. After graduating with an A.A., Marquardt transferred to California State University, Sacramento. In 1998 at the age of 25, Marquardt entered Playboy's Millennium Playmate search. She had a successful photo shoot and was sent to the Playboy Mansion for another test shoot. Later, Marquardt graduated from CSU Sacramento with a B.A. in Communications and an emphasis on Public Relations.

In 2001, Marquardt moved to Los Angeles after earning her Master's Degree in Communications from the University of the Pacific in Stockton, California. She later took a graduate level course in broadcast journalism through UCLA Extension, which was shown on the first season of The Girls Next Door (most notably when she had to walk out of her first Playboy shoot to attend a class). On arriving in LA she started to pursue modeling and acting, and began appearing in small acting roles. After testing twice unsuccessfully for Playboy, she was invited to the Playboy Mansion and soon became a regular there. In October 2002, after more than a year of visiting the Mansion, she was invited to move in and become one of Hefner's girlfriends.

In the September 17, 2007 issue of Star magazine, Marquardt stated that she is married, but separated and has been the entire time she has lived in the Playboy mansion. According to the interview, Bridget's husband supported her move to LA and they have remained friends.

Marquardt has a cat named Gizmo and a dog named Wednesday ("Winnie") who is a Pekingese.

Marquardt is featured on the E! TV show The Girls Next Door, and appeared in a pictorial in Playboy magazine's November 2005 issue as well as the September 2006 issue. She has appeared in several films as well including the horror/comedy Kottentail in which she portrays a scientist doing genetic research on rabbits. She appeared in an episode of Curb Your Enthusiasm as herself along with Holly Madison and Hefner in 2005.

She also appeared in an episode of Celebrity Paranormal Project which aired on November 19, 2006. In the episode, she had the strongest connection with ghosts of anyone else in the group. She also claimed to have taken an online paranormal course because of her interests in paranormal activity.

She has also appeared in an episode of The Man Show in a search to find new juggies in 2002.

She also makes an appearance in the video game Playboy: The Mansion as one of Hugh Hefner's playmates.

Most recently, Bridget also appeared in Nickelback's video "Rockstar." She, as well as Kendra Wilkinson and Holly Madison show up as the lead singer mentions Playboy Bunnies. Many other celebrities took part in the video as well.