Born in Oman to Scottish parents who moved with her to Australia during her childhood, she began appearing in television commercials and came to prominence for her portrayal of Shannon Reed on the Australian soap opera Home and Away (1994–1997), for which she received two Logie Award nominations.

Her other credits include I Heart Huckabees (2004), Definitely, Maybe (2008), Keeping Up with the Joneses (2016), Tag (2018), and The Beach Bum (2019), in addition to voice roles in animated films such as Horton Hears a Who!

Fisher had a recurring role on the fourth and fifth seasons of the sitcom Arrested Development (2013–2019) and has starred in the comedy drama series Wolf Like Me since 2022.

At the age of 21, she attended L'École Internationale de Théâtre Jacques Lecoq in Paris, where she studied clown, mime, musical theatre, and commedia dell'arte.

[15] After leaving the soap, Fisher enrolled at L'École Internationale de Théâtre Jacques Lecoq, a theatre and arts training school in Paris, and went on to appear in pantomime in the United Kingdom.

[16][17] She also toured with Darren Day in the musical Summer Holiday; appeared in the London theatre production of Così,[18] and played an ill-fated member of an elite group of international students in the German slasher film Swimming Pool (2001).

[19] Fisher transitioned to Hollywood in 2002, with the part of the love interest of a cowardly slacker Shaggy Rogers in the live-action film Scooby-Doo.

In his review for the latter, David Rooney of Variety felt that Fisher "adds easy charm and a thinly developed hint of romantic interest", in what he summed as an "uneven but endearing farce about breaking into showbiz".

Fisher appeared as a Manhattan party host in the independent drama London (2005), opposite Jessica Biel, Chris Evans and Jason Statham.

She next starred in the romantic comedy Wedding Daze (2006), with Jason Biggs, playing a dissatisfied waitress who spontaneously gets engaged to a grieving young man.

[30] In the thriller The Lookout (2007), opposite Joseph Gordon-Levitt and Matthew Goode, Fisher played a woman used by a gang leader to seduce a man with lasting mental impairments.

[8] Reviewers felt the film was a "refreshing entry into the romantic comedy genre",[32] and The New Yorker wrote that the "interest lies" in the female characters, concluding: "Isla Fisher, short, with thick auburn hair, is a changeable free spirit who keeps the male lead, and maybe herself off balance".

[35] Fisher obtained her first leading film role in the comedy Confessions of a Shopaholic (2009), where she played a college graduate who works as a financial journalist in New York City to support her shopping addiction.

[36] Upon its release, the film received lukewarm reviews from critics; while Time Out described her as "silly and adorable", The Christian Science Monitor remarked: "Isla Fisher is such a bundle of comic energy that watching her spin her wheels in the aggressively unfunny Confessions of a Shopaholic counts as cruel and unusual punishment for her as well as for us".

[42] Fisher voiced a hot-tempered but good-hearted desert iguana befriending an eccentric chameleon in the 3D animated Western action comedy Rango (2011), featuring Johnny Depp, Abigail Breslin and Bill Nighy.

[45] Fisher starred in the comedy Bachelorette (2012), opposite Kirsten Dunst, Lizzy Caplan and Rebel Wilson, portraying a ditzy party girl and one-third of a trio of troubled women who reunite for the wedding of a friend who was ridiculed in high school.

In its review for the film, Daily Telegraph found Fisher to be "brilliantly slow as a hot mess whose main ambition is to get coked out of her skull".

[50] The Great Gatsby, an adaptation of F. Scott Fitzgerald's 1925 novel, directed by Baz Luhrmann, and opposite Leonardo DiCaprio, Carey Mulligan and Tobey Maguire, saw her portray an ambitious social climber and the mistress of an upper-class socialite.

[54] Fisher took on a larger role as an escapist and stage magician in the heist thriller Now You See Me, with Jesse Eisenberg, Mark Ruffalo, Woody Harrelson, Mélanie Laurent and Morgan Freeman.

[57] Also in 2013, Fisher obtained the nine-episode role of an actress in the fourth season of Arrested Development, which was released on Netflix,[58] and appeared opposite Jennifer Aniston, Tim Robbins, and Will Forte in Life of Crime, a film adaptation of Elmore Leonard's 1978 novel The Switch, as the mistress of a wealthy man who refuses to pay the ransom for his kidnapped wife.

[59] Fisher, along with the cast of Arrested Development, received a Screen Actors Guild Award nomination for Outstanding Performance by an Ensemble in a Comedy Series, and describing her work on the series as a career highlight, she said: "I've been really fortunate in my career to work with a lot of great people and get a lot of great gigs, but my favourite phone call ever was the Arrested Development one from my agent, It was very exciting".

[60] In Visions (2015), an independent horror film, Fisher starred as a pregnant woman who begins to experience supernatural manifestations after moving to a vineyard with her husband.

[69] Her third book and first children's novel, Marge in Charge, revolving around a mischievous babysitter with rainbow hair who tends to bend the rules,[70] was published in 2016.

[71] The book was met with a positive reception; Publishers Weekly noted that "spontaneity and mayhem" reign in the work,[72] while The Daily Express found "the comic tale of [the] anarchic babysitter" to be "perfect for reading aloud".