In 2007, Ehrenreich auditioned and won the role of Bennie Tetrocini in Francis Ford Coppola's Tetro. Coppola requested Ehrenreich read a passage from The Catcher in the Rye for his main audition. The film was released in limited release in 2009 and received generally positive reviews from critics, who praised Ehrenreich's performance. In 2011, he played a minor role in Coppola's subsequent film Twixt and appeared alongside Natalie Portman in the Sofia Coppola-directed Miss Dior Cherie commercial.

Ehrenreich began acting at the Palisades Elementary School in Pacific Palisades, Los Angeles, and continued doing so at Crossroads School in Santa Monica, California. After graduating from high school, he studied acting at New York University, but never finished his degree. In 2009, he co-founded "The Collectin" with his friend Zoë Worth in New York that consists of actors, Writers, producers and Directors who collaborate on films and theater performances.

In 2013, he starred as Ethan Wate in the film adaptation of the novel Beautiful Creatures, and appeared as Whip Taylor in Park Chan-wook's thriller film Stoker. He then played the stepson of Cate Blanchett in the Woody Allen-directed drama film Blue Jasmine. In 2016, Ehrenreich became more widely known for his co-leading role as Hobie Doyle in the Coen brothers film Hail, Caesar!, alongside a cast that included Josh Brolin and George Clooney. Many critics praised Ehrenreich's performance in particular. That same year, Ehrenreich starred in the leading role of Frank Forbes in Warren Beatty's romantic comedy-drama Rules Don't Apply. He then starred in The Yellow Birds with Tye Sheridan, Jack Huston, and Jennifer Aniston, which premiered at the 2017 Sundance Film Festival.

In March 2016, The Hollywood Reporter reported that Ehrenreich was one of a number of actors to audition for the role of Han Solo for the upcoming Star Wars anthology film, and had made the final shortlist. On April 16, 2016, Deadline.com reported that he was the frontrunner for the role following a series of secret screen tests. On May 5, 2016, Ehrenreich was cast as Han Solo, with the film following Solo's early life before the events of the original 1977 Star Wars. Despite winning the role, Lucasfilm later hired an acting coach for Ehrenreich, as they were unhappy with his performance prior to this decision.