McNamara began her acting career on stage in Kansas City. She then participated in motion picture productions filmed in the Kansas City area, such as Matchmaker Mary in 2008 and the short film "Get Off My Porch". In 2010, she appeared in the 2009 Broadway revival of A Little Night Music with Catherine Zeta-Jones and Angela Lansbury. She began making guest appearances in television series, including ', 30 Rock, and Drop Dead Diva. McNamara appeared in theatrical movies such as New Year's Eve and in the Disney Channel original movie Girl vs. Monster, playing the role of Myra Santelli. She co-starred in the film Tom Sawyer & Huckleberry Finn, playing the role of Tom's girlfriend Becky Thatcher. McNamara also appeared in the independent filmsContest and A Sort of Homecoming. She appeared on three episodes of the Disney XD series Kickin' It, in which she had a recurring role as Claire, Kim's rival, and in two episodes of the Disney Channel series Jessie, playing Bryn Brietbart, a rival to Emma Ross. She also appeared in an episode of the Nickelodeon series The Thundermans. McNamara was cast in the MTV series Happyland as Harper Munroe, a theme park photographer. It was announced that McNamara would playing the recurring role of Kat on the third season of The Fosters in 2015. On May 6, 2015, ABC Family announced that McNamara would be playing the lead character Clary Fray in Shadowhunters, a television adaptation of Cassandra Clare's bestselling book series The Mortal Instruments. McNamara appeared in The Maze Runner film sequel, ', as Sonya, a co-leader of Group B. She reprised the role in the 2018 sequel, '. In September 2018, McNamara was cast in the seventh season of Arrow as the recurring character of Mia Smoak, the daughter of Oliver Queen and Felicity Smoak; McNamara was later promoted to a series regular for Arrows eighth and final season. In October 2019, The CW announced plans for a potential Arrow spin-off featuring Mia Smoak. A backdoor pilot for the spin-off aired as the ninth episode of Arrows final season. In October 2019, McNamara was cast as Julie Lawry in the CBS All Access limited series adaptation of Stephen King's The Stand. Principal photography on the limited series was completed in March 2020, though CBS All Access has not announced when the show will be released. During May and June 2020, McNamara participated in the making of The Untitled Horror Movie'', a movie that was shot by cast members receiving direction from Nick Simon via remote videoconferencing. This was due to restrictions necessitated by COVID-19 distancing protocols.
Songs
During the course of her career, McNamara has sung songs that were used in movies or television series in which she appeared. She wrote and sang "Chatter" for Contest, and she also appeared in a music video for that song. She wrote "My Heart Can Fly", which her character sings during a talent competition in Little Savages. She sang "Wait for You", the end credits song for A Sort of Homecoming. She also sang "Stay True", the end credits song for R.L. Stine's Monsterville: Cabinet of Souls. Her song "Ember" was played during the 20th episode of the second season of Shadowhunters. In December 2019, McNamara was featured as the voice of singer Sally Jessup in the animated Christmas special episode of the Dreamworks series Spirit Riding Free entitled "Spirit of Christmas", which premiered on Netflix. She also provided the vocals for several songs featured in the special.
Charitable works
McNamara has participated in anti-bullying efforts by describing how she was bullied as a child. McNamara has also worked with the Lollipop Theater Network, visiting children who are confined to hospitals due to the severity of their illnesses. In 2017, she recorded the song "Glass Slipper", which was used as part of a charity campaign for the United Nations Girl Up program. She also created a t-shirt with the "Glass Slipper" lyrics as part of this campaign. In 2018 and 2019, she participated in the Big Slick Celebrity Weekend, which raises donations for the Kansas City Children's Mercy Hospital. On March 31, 2020, McNamara announced that she was working on a song to be released on April 8. On April 8, the song "Just Like James" was made available in the Google Play Store, Apple's iTunes store, and Spotify. Proceeds from the song will be donated to the World Health Organization for Covid-19 relief efforts. Google will donate funds matching sales from the first 30 days. On May 8, 2020, McNamara participated in a live reading adaptation of Jane Austen's Pride & Prejudice to help raise funds for Acting for a Cause. The event's purpose was to help industry personnel impacted by COVID-19.
