Acting career
In 1969, Seymour appeared uncredited in her first film, Richard Attenborough's Oh! What a Lovely War. In 1970, she appeared in her first major film role in the war drama The Only Way. Playing Lillian Stein, a Jewish woman seeking shelter from Nazi persecution. In 1973, she gained her first major television role as Emma Callon in the successful 1970s series The Onedin Line. During this time, she appeared as the female lead Prima, in the two-part television miniseries Frankenstein: The True Story. Later appearing as Winston Churchill's girlfriend Pamela Plowden in Young Winston, produced by her father-in-law Richard Attenborough.
In 1973, she achieved international fame in her role as Bond girl Solitaire in the James Bond film Live and Let Die. IGN ranked her as 10th in a Top 10 Bond Babes list. In 1975, she was cast as Princess Farah in Sinbad and the Eye of the Tiger, the third part of Ray Harryhausen's Sinbad trilogy. Filmed in 1975, it was not released until its stop motion animation sequences had been completed in 1977. Then in 1978, she appeared as Serina in the Battlestar Galactica film, and in the first five episodes of the television series. She later returned to the big screen in the comedy Oh Heavenly Dog opposite Chevy Chase.
In 1980, she played the role of Constanze on stage in Peter Shaffer's play Amadeus, opposite Ian McKellen as Salieri with Tim Curry as Mozart. The play premiered on Broadway in 1980, running for 1,181 performances. It was nominated for seven Tony Awards, of which it won five.
Also in 1980, she was given the role of young theatre actress Elise McKenna in the period romance Somewhere in Time. Although the film was made with a limited budget, the role enticed her with a character she'd felt she knew. The effort was a break from her earlier work and marked the start of her friendship with co-star Christopher Reeve.
In 1981, she appeared in the television film East of Eden, based on the novel by John Steinbeck. Her portrayal of main antagonist Cathy Ames which won her a Golden Globe. In 1982, she appeared in The Scarlet Pimpernel with Anthony Andrews, and her Amadeus costar Ian McKellen. In 1984, she appeared nude in the film Lassiter, co-starring Tom Selleck. However, the film was a box office flop. In 1987, she was the subject of a pictorial in Playboy magazine, although she did not pose nude.
In 1988 she won the female lead in the twelve-part television miniseries War and Remembrance, the continued story from the miniseries The Winds of War, playing Natalie Henry, an American Jewish woman trapped in Europe during World War II. That same year, she won an Emmy Award for playing Maria Callas in the television movie Onassis: The Richest Man in the World.
In 1989, on the occasion of the 200th anniversary of the French Revolution, she appeared in the television film La révolution française, filmed in both French and English. Then she appeared as the doomed French queen, Marie Antoinette; her two children, Katherine and Sean, appear as the queen's children.
In the 1990s, Seymour earned popular and critical praise for her ongoing headlining role as Dr. Michaela "Mike" Quinn in the television series Dr. Quinn, Medicine Woman and its television sequels Dr. Quinn, Medicine Woman: The Movie (1999) and Dr. Quinn, Medicine Woman: The Heart Within (2001). Her work on the original series earned her a second Golden Globe Award. While working in the series, she met the man who would become her fourth husband, actor-director James Keach.
In the 2000s, she continued to work primarily in television. In 2004 and 2005, she made six guest appearances in The WB series Smallville, playing Genevieve Teague, the wealthy, scheming mother of Jason Teague (Jensen Ackles). In 2005, she returned to the big screen in the comedy Wedding Crashers, playing Kathleen Cleary, wife of fictional United States Secretary of the Treasury William Cleary, played by Christopher Walken. In spring 2006, she appeared in the short-lived The WB series Modern Men. Later that year, she guest-starred as a law school professor on an episode of the CBS sitcom How I Met Your Mother, and as a wealthy client on the Fox legal drama Justice. In 2007, she guest-starred in the ABC sitcom In Case of Emergency. She also appeared in ITV's Marple: Ordeal By Innocence, based on the Agatha Christie novel. Appearing as a contestant on season five of the American reality show Dancing with the Stars; where she finished in sixth place with her partner Tony Dovolani. Then she guest-starred in "One Life to Lose", a soap-opera-themed episode of the ABC crime dramedy Castle.
She later appeared in the Hallmark Channel film Dear Prudence (2008), the romantic comedy Love, Wedding, Marriage (2011), and the Hallmark Movie Channel film Lake Effects (2012).
In April 2016 she starred as Florence Lancaster in Noël Coward's play The Vortex, presented in Singapore by the British Theatre Playhouse. In 2022, she began playing the title role on the Irish Acorn TV series Harry Wild.
In 2020, she starred in Ruby's Choice, an Australian comedy/drama produced and directed by Michael Budd, which follows her title role, Ruby, as a woman with early dementia, and its impact on her and her family when she is no longer able to live independently and moves in with the family. The role won her the Australian screen industry Network Award for best actress. The film was released theatrically across Australia and New Zealand on 3 March 2022 and on 7 March 2022 premiered in Santa Barbara, California, at the 37th Santa Barbara International Film Festival where it was a Nominee Best International Feature Film. Seymour's 'Ruby's Choice' made the U.S. premiere at the Burbank International Film Festival (BIFF), winning Best Foreign Film and Best Feature Film. The event coincided with the honouring of the legendary filmmaker Tim Burton. 'Ruby's Choice' releasing nationwide in North America on May 7th, 2024."
Seymour then appeared in the Netflix movie, Irish Wish, released on 14 March 2024, on Netflix. Debuing at number one on Netflix's most watched films list - two days following its release.
In 2025, she began hosting an Acorn TV/BBC America series called Relative Secrets.
