Robert De Niro as George Mullen

The recipient of two Academy Awards (and a Presidential Medal of Freedom), De Niro is one of the most successful and beloved actors in film and television history.

He’s perhaps best known for his collaborations with acclaimed director Martin Scorsese, having delivered layered and combustible turns in films like Mean Streets, Taxi Driver, Raging Bull, Goodfellas, and The Irishman. But his career contains multitudes, with the actor routinely bouncing between drama (Bang the Drum Slowly, Awakenings), comedy (Meet the Parents, Analyze This), action (Heat, Ronin), and horror (Angel Heart, Cape Fear). And that still feels like we’re just scratching the surface.

In Zero Day, De Niro plays the former U.S. president leading the cyberattack investigation. “When you meet President Mullen, he’s someone the entire country feels comfortable turning to in a moment of crisis,” Oppenheim told Entertainment Weekly. “And in order for that to land right out of the gate, you need an actor with decades of goodwill and respect from the audience.”

Added Newman, “I think the part called for someone who had a certain level of gravitas, who had a legacy as one of America’s most significant actors.”

Lizzy Caplan as Alexandra Mullen

Caplan, a two-time Emmy nominee, began her career on the cult series Freaks and Geeks (1999–2000) before breaking through in earnest as Mean Girls outcast Janis Ian.

Her profile rose with roles in movies like Cloverfield (2008), Hot Tub Time Machine (2010), and the Now You See Me series (2016–present). Lately, Caplan has been focusing on TV, with leading roles on Showtime’s Masters of Sex (2013–2016), Hulu’s Castle Rock (2019), FX’s Fleishman Is in Trouble (2022), and AppleTV+’s Fatal Attraction (2023). She also appeared on the recent Party Down revival (2023), reprising her role as wry caterer Casey Klein.

As Alexandra Mullen, Caplan plays both a U.S. congresswoman and the daughter of De Niro’s former president. She’s investigating the cyberattack alongside her father but isn’t afraid to challenge him in the political arena.

“Every scene, there are layers of things going on for Alex, truly every beat of every scene. It was a challenge, but a welcome challenge,” she told UPI of the role.

Jesse Plemons as Roger Carlson

After winning hearts as Friday Night Lights‘ motor-mouthed Landry Clarke, Texas-born Jesse Plemons went on to work with some of this generation’s best filmmakers.

The actor has collaborated with Martin Scorsese (The Irishman, Killers of the Flower Moon), Paul Thomas Anderson (The Master), Steven Spielberg (The Post), Charlie Kaufman (I’m Thinking of Ending Things), Jane Campion (The Power of the Dog), and Yorgos Lanthimos (Kinds of Kindness). For his efforts, Plemons has been nominated for an Academy Award, a Golden Globe, and three Primetime Emmys. Mark our words: He’ll win one someday.

Plemons plays Roger Carlson on Zero Day, a stylish, ambitious aide to De Niro’s George. It’s a change of pace for Plemons, whose career has often found him playing good ‘ol boys. Speaking with The Times, he said Roger “felt a little like a talent agent to me, where your whole purpose is to protect. I’ve never played anyone like that.”

Joan Allen as Sheila Mullen

Joan Allen was a staple of Chicago’s world-famous Steppenwolf Theatre in the late ’70s before lighting up the big screen in films like Manhunter (1986), Peggy Sue Got Married (1986), The Ice Storm (1997), and Face/Off (1997). In addition to winning a Tony and a Canadian Screen Award, she’s been nominated for three Oscars, three Golden Globes, and three Primetime Emmys.

Allen plays Sheila Mullen, a nominee to the federal bench who is also George’s wife. She told Vanity Fair that George and Sheila aren’t that unlike Bill and Hillary Clinton. Allen elaborated on that point to PEOPLE, saying that the couple served as “a benchmark, or just kind of an indicator of this kind of relationship.” 

Connie Britton as Valerie Whitesell

Britton’s popularity reached new heights thanks to her Emmy-nominated role as Tami Taylor on Friday Night Lights (2004–2011), but her career began in earnest a decade earlier on the ABC sitcom Spin City.

In between roles in films like Bombshell (2019) and Promising Young Woman (2020), Britton has led several popular series, including American Horror Story (2011), Nashville (2012–2018) and The White Lotus (2021).

On Zero Day, she plays Valerie Whitesell, George’s former chief of staff. “She comes back because there is this great need — this commission George Mullen has been asked to lead is unprecedented and, frankly, nobody trusts anyone,” Britton told Tudum. “But there is great trust between President Mullen and Valerie.” 

Bill Camp as Jeremy Lasch

Before he became a consistent presence on film and TV, veteran actor Bill Camp tread the boards on and off Broadway.

He acted alongside Philip Seymour Hoffman and Andrew Garfield in Mike Nichols’ 2012 revival of Death of a Salesman and scored a Tony nomination for his turn in Broadway’s 2016 production of The Crucible, which also starred Saoirse Ronan and Ben Whishaw. He didn’t win the Tony, but he did win an Emmy that same year for his role on HBO’s The Night Of. Since then, he’s appeared in numerous films (Vice, Joker) and series (The Outsider, The Queen’s Gambit).

Camp plays Jeremy Lasch, the director of the CIA, in Zero Day. According to Netflix, he’s “the ultimate insider,” and can “either be a dangerous enemy or a valuable friend to Mullen and everyone in his circle.” Yep, that sounds like the CIA.

Dan Stevens as Evan Green

Stevens made the masses swoon as Downton Abbey‘s Matthew Crawley (2010–2012) before making a hard pivot with 2014’s thriller The Guest.

Though he’s appeared in crowd-pleasing fare (Beauty and the Beast, Night at the Museum: Secret of the Tomb), he’s become an unlikely scream king, having starred in recent horror movies like The Rental (2020), Cuckoo (2024), and Abigail (2024), not to mention Godzilla x Kong: The New Empire (2024).

He’s playing a similarly scary character in Zero Day. His Evan Green is the obnoxious host of a political talk show, the kind that’s had folks asking if he modeled the character after right-wing firebrands Tucker Carlson or Ben Shapiro. “It’s none of those people. It’s all of them,” he told Variety. “We’re in a parallel universe with this story, and sure, there are reflections on certain administrations that you can look for, and comparisons are going to be plenty.”

Angela Bassett as President Evelyn Mitchell

Bassett is one of the most celebrated actresses of her generation, having been named one of the 100 most influential people in the world by Time in 2023. She’s also the recipient of a Primetime Emmy, two Golden Globes, two Academy Award nominations, and an Academy Honorary Award.

You can see some of her best work in Malcolm X (1992), What’s Love Got to Do With It? (1993), Strange Days (1995), and the Black Panther films, the second of which scored her most recent Oscar nomination. Currently, she’s an executive producer and star of ABC’s 9-1-1.

Bassett plays no less than the U.S. president on Zero Day (a position she’s also carrying in this year’s Mission: Impossible – The Final Reckoning).

Speaking with Town & Country, co-creator Newman explained the difficulty of casting someone who could convey authority as well as De Niro. “We knew the challenge would be having a former president being called in to see the current president — and the current president’s got to be in the slightly higher chair,” he said. “But when your former president is Robert De Niro, who are you going to get who you’ll watch and think, ‘Oh, here’s someone who can tell him what to do.’”

Matthew Modine as Richard Dreyer

Since breaking out as the star of Robert Altman’s Streamers (1983), Matthew Modine has worked with everyone from Stanley Kubrick and Jonathan Demme to Spike Lee and Christopher Nolan. He’s even relevant among Gen Z audiences, having played Dr. Martin Brenner on Stranger Things (2016–2022).

Speaking with PEOPLE, Modine described his process of prepping to play House Speaker Richard Dreyer as like “a witch making a brew.” He added, “I threw a little bit of this one, a little bit of that one, stirred it up and then put the mask on.”