2000–2019: Television roles and acclaim
In 2000, Smart was cast as Lana Gardner in the critically acclaimed NBC comedy series Frasier, acting opposite Kelsey Grammer, set in her hometown of Seattle. She went on to win two Primetime Emmy Awards for Outstanding Guest Actress in a Comedy Series. Reflecting on the role, Smart said: "I had loved that role on Frasier so much, particularly that first episode. It's nice to get nominated and win for something you were particularly proud of. At the time, I was a little bit snobby about doing guest parts. Based on what, I don't know. It wasn't something I was seeking. But my agent said, 'You have to read this.' I thought it was hilarious, and the show was brilliant, so I didn't even hesitate. I remember when we did the table read with the rest of the cast, we could hardly get through it we were laughing so hard."
The same year, she was in the company of the second Broadway revival production of The Man Who Came to Dinner, which earned her a Tony Award nomination. Soon after, she landed roles in several high-profile films including Sweet Home Alabama (2002), playing the mother-in-law of Reese Witherspoon, and in the comedy Bringing Down The House (2002), opposite Queen Latifah. She also had a supporting role in the independent drama Garden State (2004). Between 2000 and 2004, Smart played the role of Supervisor of Detectives and ex-wife to Chief Jack Mannion of the Metropolitan Police Department on The District. From 2002 to 2007, she voiced Dr. Ann Possible in Kim Possible, and also provided the voice of the alcoholic chain-smoking, Pickles Oblong, on The Oblongs. In 2004, she reprised her voice role as Reba Heyerdahl in an episode of the Nickelodeon series Hey Arnold!. The same year, she was cast in a lead role in the short-lived Center of the Universe. She also had a supporting role in David O. Russell's I Heart Huckabees (2004).
In January 2006, Smart joined the cast of the Fox series 24, playing the mentally unstable First Lady of the United States, Martha Logan, to actor Gregory Itzin's President Charles Logan. She received back-to-back Emmy nominations for Outstanding Supporting Actress in a Drama Series and Outstanding Guest Actress in a Drama for the role in 2006 and 2007. She also appeared in several films between 2006 and 2010, including the Curtis Hanson drama, Lucky You (2007), opposite Drew Barrymore; Youth in Revolt (2009); and the independent comedy Barry Munday (2010). Smart won her third Emmy Award for Best Supporting Actress in a Comedy Series for portraying Samantha's overbearing mother in the sitcom Samantha Who?, opposite Christina Applegate, which she played from 2007 to 2009. She later was cast as Hawaii Governor Pat Jameson during the first season of the CBS-TV remake of Hawaii Five-0. In 2012, Smart was nominated for a Primetime Emmy Award for Outstanding Guest Actress in a Drama Series for her role in Harry's Law. She then had a supporting role in the Lifetime film Call Me Crazy: A Five Film (2013).
In 2015, Smart starred in the second season of the FX television series Fargo as Floyd Gerhardt. Floyd's husband heads Fargo's most prominent organized crime syndicate, and she is forced to take over after her husband suffers a debilitating stroke. She later finds herself having to lead the Gerhardt dynasty and deal with her sons, who are vying to replace their father. For her performance, Smart won the Critics' Choice Television Award for Best Supporting Actress in a Movie/Miniseries and was nominated for the Primetime Emmy Award for Outstanding Supporting Actress in a Limited Series or Movie. She worked with Hawley again on Legion, in which she played Melanie Bird, a therapist who works with the eponymous character. In 2016, Smart had a role in the thriller The Accountant, opposite Ben Affleck, Anna Kendrick, and John Lithgow. In 2018, Smart played a guardian angel, to co-star Candace Cameron, in the Hallmark Channel television film A Shoe Addict's Christmas, which aired Sunday November 25, 2018.
In 2019, Smart portrayed Laurie Juspeczyk, the former Silk Spectre, in the HBO superhero drama limited series Watchmen based on characters from the graphic novel of the same name. Smart's performance was singled out by critics including Eric Deggans of NPR who described her performance as "compelling" and "the always-excellent Jean Smart [playing] a cynical, heroically-damaged middle-aged version of Laurie Juspecyk." The series received critical acclaim, winning 11 Primetime Emmy Awards, including Outstanding Limited Series. Smart was nominated for Primetime Emmy Award for Outstanding Supporting Actress in a Limited Series or Movie and received the Critics' Choice Television Award for Best Supporting Actress in a Drama Series for her performance.
