Katherine McNamara was born in Kansas City, Missouri, to parents Ursula and Evan McNamara. She grew up in Lee’s Summit, Missouri, and later moved to Los Angeles in 2011 to pursue her acting career. McNamara was a talented student, advanced in certain subjects, and thus partly homeschooled. She gained her high school diploma at the age of 14. By 17, McNamara had graduated summa cum laude with her bachelor’s degree in Business Administration from Drexel University. She began acting on stage at a very young age in Kansas City. She later participated in movies filmed in the city, like “Matchmaker Mary” (2008).
In 2010, she appeared in the Broadway revival of “A Little Night Music” alongside Catherine Zeta-Jones. Around this time, McNamara also began making appearances on several television shows like “30 Rock,” “Drop Dead Diva,” and “Law & Order: SVU,” and films like “New Year’s Eve,” “Girl vs. Monster,” “Tom Sawyer & Huckleberry Finn,” and “Contest.” She also briefly appeared on the Disney XD series “Kickin’ It,” the Disney Channel series “Jessie,” Nickelodeon’s “The Thundermans,” and M.T.V.’s “Happyland.” In 2015, McNamara announced that she would play the role of Kat in the third season of “The Fosters.” The same year, she was cast to play Clary Fray in ABC Family’s “Shadowhunters,” based on the bestselling book series “The Mortal Instruments” by Cassandra Clare. McNamara also became part of the film adaptations of “The Maze Runner” trilogy, playing the character of Sonya in “Maze Runner: The Scorch Trials” and “Maze Runner: The Death Cure.” In September 2018, she was cast to play the role of Mia Smoak in the seventh season of CW’s “Arrow.” Smoak is the daughter of Oliver Queen and Felicity Smoak, who travels to the past. The character became a series in the show’s eighth and final season. She later reprised her role in the five-episode-long “Armageddon” storyline in the eighth season of CW’s “The Flash.” 2019 saw McNamara as Julie Lawry in the limited series adaptation of Stephan King’s “The Stand.” She has also hosted the horror podcast “The Burned Photo” and “Return to the Shadows,” a “Shadowhunters” rewatch podcast. In March 2022, she was cast to play the role of Abby Walker in “Walker: Independence,“ a prequel to “Walker.” She also had a brief singing career, creating songs for the projects she’s acted in.
McNamara is also known for her philanthropy. She has participated in anti-bullying efforts, the United Nations’ Girl Up campaign, and Covid-19 relief efforts. In 2020, she also participated in a live-reading of Jane Austen’s “Pride & Prejudice” with Acting for a Cause.