In the movie adaptation of The Hunger Games, Ludwig played Cato, the fierce male tribute from District 2, the primary threat to the protagonists’ lives during the 74th Hunger Games. The film was released worldwide on March 23, 2012. Ludwig won the award for Best Fight on 2012 MTV Movie Awards along with Jennifer Lawrence and Josh Hutcherson, as well as the award for Best Villain at the 2012 Teen Choice Awards. Ludwig released his first single “Liv It Up (Teenage Wasteland)” on March 1, 2012. In 2013, he co-starred in the films Lone Survivor and Grown Ups 2. In 2014, he became a part of the main cast of the popular TV series Vikings, playing the character of Björn Ironside, the son of Ragnar Lothbrok and Lagertha.

In 2015, he had the male lead in both the horror films Final Girl and The Final Girls, which are unrelated to each other. He played the pacifist hacker Dorn in 2020’s Bad Boys for Life, and also appeared in The Band Perry’s music video for “Gentle on My Mind” alongside Teen Wolf actress Shelley Hennig.

Ludwig was a competitive freestyle skier, and has participated in skydiving. In February 2019, Ludwig came clean about his battle with depression, anxiety, alcoholism, and substance abuse from the young age of 14. He shared his story of going through rehab and finding a new identity for BITE THE BULLET Stories.