Thiessen participated in beauty pageants during her childhood and was crowned Miss Junior America in 1987. The following year, she appeared on the cover of
Teen magazine, having won the magazine's "Great Model Search". In 1989, she was named
Cover Girls "Model of the Year", and landed her first role of
Kelly Kapowski on
NBC's television sitcom
Saved by the Bell, starring until its end in 1993. The success of the show gave her career a boost and Thiessen received
Young Artist Award nominations for
Outstanding Young Ensemble Cast in 1990 and
Best Young Actress Starring in an Off-Primetime Series in 1991 and 1993. Thiessen was Spelling's first choice to replace Doherty in the series
Charmed in 2001, but she refused his offer because she was hoping the NBC pilot for
Everything But the Girl would be picked up. The role eventually went to
Rose McGowan. Meanwhile, Thiessen starred in direct-to-video parody film
Shriek If You Know What I Did Last Friday the Thirteenth (2000) and in television movie
Everything But the Girl (2001), before appearing in the
Woody Allen-directed film
Hollywood Ending (2002) and starring in action-drama series
Fastlane (2002–03) as Wilhelmina 'Billie' Chambers, for which she received a
Teen Choice Award nomination for
Choice TV Actress – Drama/Action Adventure. which earned distinctions at several film festivals, including winning Best Score at the Rhode Island International Film Festival, an Academy Award qualifying festival. The original motion picture soundtrack album, co-produced by Thiessen and Al Gomes of Big Noise, was placed on the Official Ballot for the 49th Annual Grammy Awards by The Recording Academy in several categories including Best Compilation Soundtrack Album For Motion Picture, Television or Other Visual Media. Later on, she starred in television movies
Stroller Wars (2006) and
Pandemic (2007), she joined the cast of
ABC's drama
What About Brian (2007) for its last five episodes and starred in the science fiction film
Cyborg Soldier (2008). In 2008, she made her second music video appearance, this time for
Ben Lee's "American Television". Thiessen appeared with her husband
Brady Smith on the September 6, 2009 episode of season four of the reality show
HGTV Design Star. Interior designer Lonni Paul, one of the final three contestants of the season, was given the task of redesigning Thiessen's guest bedroom with an eco-friendly theme; Thiessen and Paul now have a nursery furniture line called PetitNest. From 2009 through 2014, Thiessen appeared in the
USA Network crime series
White Collar as
Elizabeth Burke. in 2010|253x253px On February 4, 2015, Thiessen reunited with
Saved By the Bell co-stars
Mark-Paul Gosselaar,
Elizabeth Berkley,
Dennis Haskins and
Mario Lopez on
The Tonight Show Starring Jimmy Fallon, in which they appeared in a
Saved by the Bell sketch with host
Jimmy Fallon. In the same year, Thiessen started hosting her own show on
Cooking Channel called ''
Dinner at Tiffani's'', which ran until 2017. On June 7, 2017, Thiessen was cast as Lori Mendoza, mother of the Mendoza family on the multi camera
Netflix sitcom
Alexa & Katie, which premiered its first two seasons on March 23 and December 26, 2018. In 2021, at the
48th Daytime Creative Arts Emmy Awards, she was nominated in the category of Outstanding Performance by a Supporting Actress in a Daytime Fiction Program. The show premiered on
NBCUniversal's streaming network
Peacock beginning November 2020. In November, it was announced that Thiessen would host the
MTV comedy clip show Deliciousness, a spinoff of that network's previous program,
Ridiculousness. ==Charity work==