Sarsgaard has acted in films, such as Garden State, Kinsey (both 2004), Jarhead, Flightplan (both 2005), Elegy (2008), An Education, Orphan (both 2009), Lovelace, Blue Jasmine (both 2013), Black Mass (2015), Jackie (2016), and The Lost Daughter (2021).

[9] Following his graduation from Fairfield Prep in 1989, he attended Bard College in New York for two years before transferring to Washington University in St. Louis (WashU) in 1991, where he co-founded an improvisational comedy troupe "Mama's Pot Roast".

[9] While at WashU, Sarsgaard began performing in plays in an offshoot of New York's Actors Studio;[9] His first role was as the servant Laurent in Molière's Tartuffe.

[13][14] In 1995, Sarsgaard made his theatrical debut in the Off-Broadway production of Horton Foote's Laura Dennis, which was directed by James Houghton.

[15] Ben Brantley of The New York Times wrote: "Mr. Sarsgaard ... emerges as an actor to watch with a performance of breathtaking emotional conviction.

[19] He received a substantial role in the 1998 film The Man in the Iron Mask, where he played Raoul, the ill-fated son of John Malkovich's dueling Musketeer, Athos.

[20] The film uses characters from Alexandre Dumas' d'Artagnan Romances, and is very loosely adapted from some plot elements of The Vicomte de Bragelonne.

[23] In 1999, Sarsgaard earned critical recognition in Kimberly Peirce's Boys Don't Cry, where he was cast as notorious killer John Lotter.

The film is based on the real-life story of Brandon Teena, who was raped and murdered in 1993 by Lotter and Tom Nissen after they found out that he was a trans man.

According to The Boston Globe, "Peter Sarsgaard ... makes the killer's terrible trajectory not only believable, but grounded in the most mundane clodhopper behavior.

[29] His first leading role was in the 2001 feature The Center of the World, where he plays Richard Longman, a lonely young entrepreneur who skips out on his company's big initial public offering and pays a stripper (Molly Parker) $10,000 to fly to Las Vegas with him.

Scott of the New York Times, reported that the performances by both Sarsgaard and Parker "provide a rough grain of authenticity, capturing the blunted affect and aimless neediness of people in their 20s struggling to navigate a world of material abundance and impoverished emotional possibility.

"[30] Scott concluded in his recap that Sarsgaard made his character "seem like a genuinely nice guy, too innocent to grasp the sleaziness of his bargain with Florence.

[41] The newspaper concluded with, "The character doesn't seethe with personal resentment; when he does a slow burn, he conveys a much deeper sense of a man's value system being violated past the breaking point.

[46] Paul Clinton of CNN reported that Sarsgaard's Clyde Martin "stands out" and "confirms that he's without doubt one of the best character actors of his generation.

[6] In 2005, Sarsgaard starred in the drama The Dying Gaul, where he plays Robert Sandrich, a struggling screenwriter who has written a serious love story about a man and his terminally ill partner.

[54] One sketch featured the severe acute respiratory syndrome (SARS) global scare, which was still fresh in many minds, and one of the skits included a promotion for the Peter Sarsgaard "SARS-Guard", a reference to facemasks.

Year of the Dog is a dark comedy about a lonely middle-aged woman, played by Molly Shannon, who finds that animals are the only beings she can truly rely on.

[61] In 2008, Sarsgaard made his Broadway debut at the Royal Court Theatre of Anton Chekhov's adaptation The Seagull alongside Kristin Scott Thomas, Mackenzie Crook and Carey Mulligan.

His next film appearance was in the thriller Orphan, where he and Vera Farmiga play a married couple who lose a baby and adopt a nine-year-old girl, who is not as innocent as she claims to be.

"[72] Sarsgaard played Mikhail Lvovich Astrov, a country doctor and philosopher, in the Classic Stage Company's 2009 off-Broadway production of Anton Chekhov's Uncle Vanya in New York City.

[73][74] Joe Dziemianowicz of the New York Daily News gave the production one out of four stars, but complimented his performance, writing that Sarsgaard does a "credible job as the doctor".

[75] In the Bloomberg review of Uncle Vanya, John Simon, wrote: "Sarsgaard can't find the right tempi or emphases: shuttling between colorless rattle and silence-studded rallentandos, he fails at both infectious enthusiasm and self-effacing charm.

"[76] Sarsgaard played a federal agent in the action comedy film Knight and Day, released in June 2010, in which he appeared alongside Tom Cruise and Cameron Diaz.

[81] Sarsgaard also appeared in the American TV series The Killing (2013) as a man on death row perhaps wrongfully convicted for the brutal murder of his wife, a performance which he said included "some of the best acting I have ever done in my life.

Sarsgaard then took a role as Martin Schmidt in the Hulu limited series The Looming Tower (2018), earning a nomination for the Critics' Choice Television Award for Best Supporting Actor in a Movie/Miniseries.

He returned to television in another Hulu miniseries Dopesick (2021) playing Rick Mountcastle, for which he received a Primetime Emmy Award for Outstanding Supporting Actor in a Limited or Anthology Series or Movie nomination.

[84] Sarsgaard appeared in The Lost Daughter (2021), directed by his wife Maggie Gyllenhaal, and the following year played the role of District Attorney Gil Colson in The Batman (2022).

"[9] Among his most notable romantic relationships, Sarsgaard dated burlesque dancer Dita Von Teese[86] and model and actress Shalom Harlow.