Dylan O’Brien was born in New York City, the son of Lisa (née Rhodes), a former actress who also ran an acting school, and Patrick, a camera operator. He grew up in Springfield Township, New Jersey, until the age of twelve, when he and his family moved to Hermosa Beach, California. His father is of Irish descent, and his mother is of Italian, English and Spanish ancestry. After graduating from Mira Costa High School in 2009, he considered pursuing sports broadcasting and possibly working for the Mets. He planned to attend Syracuse University in fall 2009 as a sports broadcasting major, but decided to move to Los Angeles for an acting career. At fourteen, Dylan began posting original videos onto his YouTube channel. With the videos developing, a local producer and director approached him about doing work for a web series of hers. While working on the webseries, Dylan met an actor who connected him with a manager.

He went through several auditions before getting one of the main roles in MTV’s Teen Wolf, a series loosely based on the 1985 film of the same name. He was originally intended to play Scott, but after reading the script, Dylan wanted to audition for the part of Stiles instead. After four auditions he was cast. In 2010, he successfully played Stiles in the series. In 2013, Dylan co-starred in the comedy film The Internship, with Vince Vaughn and Owen Wilson.

Dylan played Thomas in the lead role in The Maze Runner, a film adaptation of the novel of the same name, which began filming in summer 2013, while he was on hiatus from Teen Wolf. Yahoo! Movies named him as one of the 15 Breakout Stars to Watch for in 2014. Filming for the Maze Runner sequel, Maze Runner: The Scorch Trials, began at the end of October 2014 in New Mexico, and the film was released in September 18, 2015.

Dylan produced, directed and starred in a number of comedic short films which he released through his personal YouTube channel. He was the drummer for the independent rock band Slow Kids at Play.