Hedges then starred as an aggressive youth in an off-Broadway production of Yen and had supporting roles in the coming-of-age film Lady Bird and the drama Three Billboards Outside Ebbing, Missouri in 2017.

In 2018, Hedges played the lead role of a teenager forced into a gay conversion therapy program in Boy Erased, which earned him a nomination for the Golden Globe Award for Best Actor in a Drama.

[16][17] He went on to play small roles in the comedy-drama Arthur Newman (2012),[18] Jason Reitman's romance Labor Day (2013),[19] and Terry Gilliam's science fiction film The Zero Theorem (2013).

[20][21] In 2014, Hedges had a minor role in Anderson's The Grand Budapest Hotel and played the son of Jeremy Renner's character in Michael Cuesta's drama Kill the Messenger, which was based on CIA involvement in Contra cocaine trafficking.

[26] Tim Robey of The Daily Telegraph wrote, "Hedges, phenomenal, fights off every cliché of 'troubled' teenagerhood and gives us a gruff, sympathetic boy with a tearaway sex drive.

[32] Taking note of his performance as an aggressive and violent teenager who shares a troubled relationship with his half-brother, Ben Brantley of The New York Times wrote that he "delivers an expert anatomy of an adolescent on the edge of explosion".

[34][35][36][37] Also in 2017, Hedges had supporting roles in two films—Greta Gerwig's directorial debut Lady Bird and Martin McDonagh's crime drama Three Billboards Outside Ebbing, Missouri, both of which were nominated for the Academy Award for Best Picture.

[46] In Ben Is Back, a drama directed by his father and co-starring Julia Roberts, he played the titular character, a drug addict who returns home after spending time in rehab.

Pete Hammond of Deadline Hollywood praised both Roberts's and Hedges's performances, adding that they "are pitch perfect together, never striking a false note in demonstrating the everlasting bond between a mother and son.

Reviewing the film for Entertainment Weekly, Leah Greenblatt wrote that Hedges "doesn’t seem to have found a role yet he can’t fully inhabit; his Otis is raw and furious, and genuinely funny.

"[51] He next took on a supporting part in Trey Edward Shults' Waves, a drama about the emotional journey of a suburban family,[52] which led Peter Debruge of Variety to consider it "an impactful reminder of how much the actor can bring to a smaller role".

[58] Hedges took a small break from acting to focus on writing, and returned to the stage in a 2023 West End theatre production of Brokeback Mountain at @sohoplace, in which he starred as Ennis Del Mar opposite Mike Faist's Jack Twist.

[62] Commenting on his role as a kind neighbour of the film's troubled protagonist (played by Victor), Peter Debruge considered it "perfectly suited to Lukas Hedges’ uniquely sensitive energy".