Casting
Quantico had a racially diverse cast as FBI recruits who deal with their individual problems. Safran had wanted the series to be diverse from the beginning, saying,
"You're not just watching people who have struggled to achieve places of power and they're there. This show is about the struggle to achieve that. Their politics and their racial makeup and their religious backgrounds are very important to their characterizations and who they are. I really am interested in looking at how every culture handles stress — and in particular, how people from all these different backgrounds find their place in the FBI, an agency that has historically-fraught relationships with gay people and people of color."
The first actor cast in the series was Tate Ellington as FBI trainee Simon Asher. Graham Rogers was then cast as another FBI trainee, Caleb Haas. It was announced that Aunjanue Ellis had signed to play Miranda Shaw, assistant director and training supervisor of the academy. Dougray Scott was cast as Liam O'Connor, Miranda's former partner and current subordinate.
Indian actor Priyanka Chopra was cast as series protagonist Alex Parrish, the result of a talent holding deal with ABC Studios which required the company to develop a starring project for her or cast her in an existing project for the 2015 television season. ABC casting executive Keli Lee had long tried to persuade Chopra to perform on television in the United States. When the actress began considering U.S. TV, Lee learned that Chopra had been approached by another studio: "I said [to Chopra], 'No, you can't make this deal elsewhere. You're coming here. And I'm flying to India.'" Lee went to India and convinced Chopra to accept ABC's offer. The actress said about Lee: "I told her, the only way I would do it is if you find me a show and a path which first will put me in the same position that I am in India."
Chopra saw the deal as an opportunity to represent South Asia and challenge Indian stereotypes in Hollywood and the United States, saying,
"When I was in school [in the U.S.], you never saw anyone who looked like us that was on TV. And that was really weird for me because there's so many people of South Asian descent in America – in the world. I didn't want to be this stereotype of what Indian people are usually seen as in global pop culture. We don't just have to be Apu from The Simpsons." After being given all 26 pilot scripts which ABC was filming for the 2015–2016 television season, she chose Quantico. Despite having appeared in more than 50 films, she was required to audition for the first time, which she found nerve-wracking.
Safran was impressed by Chopra's audition, which helped him re-envision the character, adding,
"She walked into the room, and it was like the molecules shifted in that way that superstars have. I was very confused because I didn't know who she was, but we all sat up straighter. We're like, this is clearly a movie star; it's like every hair on the back of your neck stands up watching her act. When I went back home I couldn't think about anyone else." Chopra became the first South Asian to headline an American network drama series.
Jake McLaughlin was chosen to play Ryan Booth, Alex's love interest, and Johanna Braddy and Yasmine Al Massri were cast in the final co-starring roles of trainees Shelby Wyatt and Nimah and Raina Amin. ABC announced after it picked up the pilot that the Liam O'Connor character would be re-cast with Josh Hopkins replacing Dougray Scott in July 2015. That month, it was announced that Anabelle Acosta was cast in a recurring role for a multi-episode story arc as Quantico recruit and former police officer Natalie Vasquez. Rick Cosnett was also signed for a recurring role as Elias Harper, a former defense attorney-analyst recruit. Prior to the premiere, Acosta was promoted to a series regular. In September 2015, Jacob Artist was cast in a recurring role as Brandon Fletcher, an FBI agent-in-training. Marcia Cross was cast as Senator Claire Haas, vice presidential candidate, Caleb's mother, and the wife of FBI Deputy Director Clayton Haas. In November, Jay Armstrong Johnson, Lenny Platt and Li Jun Li were cast as recurring characters who would be added after the mid-season break.
Following the season one finale, Safran confirmed that all series regulars would return for the second season, except for Acosta, Ellington and Hopkins, whose characters were killed off. Safran also expressed interest in bringing back Cross' Claire Haas after it was revealed that she was involved in the bombing plot. Safran discussed the return of Henry Czerny, who played CIA director Matthew Keyes in the season one finale, since the character was important to the storyline. In July 2016, Czerny joined the cast in the recurring role. The series added three regulars to the cast: Russell Tovey as Harry Doyle, Blair Underwood as CIA officer Owen Hall and Pearl Thusi as type-A attorney Dayana Mampasi. In July 2016, Aarón Díaz joined the series in a recurring role as photojournalist León Velez, and it was reported that Tracy Ifeachor and David Lim were cast in recurring roles as Lydia Hall and Sebastian Chen. In early 2017, Hunter Parrish and Krysta Rodriguez were cast in the recurring roles of Clay Haas and Maxine Griffin.
After the third season renewal announcement, it was reported that Al Massri and Thusi would leave the series, and in June 2017, it was reported that Ellis and Tovey would not return as part of a creative overhaul. However, in August 2017, it was confirmed that Tovey would in fact be returning as a series regular. In late July 2017, Marlee Matlin joined the show as a series regular in the role of ex-FBI agent Jocelyn Turner in the third season. Alan Powell joined the cast in November 2017 as series regular Mike McQuigg, an undercover agent. The next month, Amber Skye Noyes joined the third season in the recurring role of Celine Fox. In January 2018, Vandit Bhatt joined in the recurring role of Jagdeep Patel. On February 16, 2018, it was confirmed that Aunjanue Ellis had exited the series.
