Matthew Daddario was first seen in the 2012 short film ‘The Debut,’ directed by Tatianna Kantorowicz. He was next seen in the 2013 American romantic drama film ‘Breathe In’ where he played the role of ‘Aaron.’ The film saw mixed reviews upon release. That same year, he also appeared in the American comedy-drama film ‘Delivery Man,’ directed by Ken Scott. The film opened to a mixed reception and was a commercial success. In 2014, he starred as ‘Danny Ladouceur’ in the Thomas Carter-directed American sports drama film ‘When the Game Stands Tall.’ The film received mixed reviews from critics and grossed over $30.1 million against a budget of $15 million. The following year, he was seen playing the role of ‘Gabriel’ in the American romantic comedy-drama film ‘Naomi and Ely's No Kiss List,’ directed by Kristin Hanggi. In 2016, he joined the main cast of the American supernatural drama television series ‘Shadowhunters.’ He played the role of ‘Alec Lightwood’ in the series which earned him 2 ‘Teen Choice Awards.’ ‘Shadowhunters’ ran for 3 seasons and aired its final episode in May 2019.
In 2016, Daddario also appeared in the American horror film ‘Cabin Fever,’ directed by Travis Z. The film was met with overwhelmingly negative reviews and was given a 0% rating on Rotten Tomatoes. In 2020, he was seen in the episode "To Take a Hostage" of the American police procedural crime drama television series ‘Tommy.’ In 2021, he was seen playing the role of ‘Scooter’ in the American dark comedy-drama anthology television series ‘Why Women Kill.’ That same year, he also starred in the American erotic romantic drama film ‘Trust,’ directed by Brian DeCubellis.