Timothée Chalamet had to lose 25 lbs for his role as Nic Sheff. He also had a consultant and doctor on set to ensure his acting as a drug addict was realistic and authentic.
The first scenes shot for the film were the most intense, according to Van Groeningen, and involved Chalamet's character being hospitalized for a drug-overdose. Chalamet was instructed to lose weight a couple weeks before the filming of the "hospitalization scenes", and subsequently rested to recover in order to complete the rest of the shoot. Chalamet has stated that there were numerous "doctor visits" and "close calls" during the shoot, saying "Your mind knows you're acting. But when you drop twenty pounds and you are under a rain machine for eight takes in a T-shirt, your body doesn't know you're acting."
The real Nic Sheff stated in a Q & A that the drawing book that David, Steve Carell in the movie finds of his son's addiction struggles was drawn by Nic's real life half brother Jasper Sheff.
The title of this film (and the book it is based upon) comes from John Lennon's song "Beautiful Boy (Darling Boy)". Author David Sheff famously interviewed John Lennon and Yoko Ono in the months leading up to the release of their album, "Double Fantasy" in 1980. John Lennon was murdered 3 weeks after its release, on Dec. 8, 1980.
Co-screenwriter Luke Davies is himself a recovering addict. During the 80s, Davies developed a dependency on heroin, which led him on a path of self-destruction. He managed to overcome his addiction in 1990, and later turned his experiences into the novel "Candy", published in mid-1998. The novel was later turned into a film in 2006, with Davies co-penning the screenplay.
The movie is a combination of Nic Sheff's book Tweak and his father David's book Beautiful Boy: A Father's Journey Through His Son's Addiction.
The editing of the film took 7 months in total, during which the movie was completely recut multiple times. Initially Nico Leunen, Van Groeningen's long-time collaborator, was not involved in the project; however, Van Groeningen became dissatisfied with the editing process and brought Leunen to Los Angeles to reconstruct the film.
One of the scenes with Jack Dylan Grazer and Steve Carell was shot at a school beside a hill with sheep living on it. While filming, the sheep interrupted the shot by making noises and bleating for approximately 30 minutes
Steve Carell and Amy Ryan previously appeared together as a couple in The Office (US).
Prior to filming, Van Groeningen arranged for two weeks of rehearsals with the cast, a common practice in Flemish productions but not in Hollywood.
Timothée Chalamet shot this film after he did Lady Bird, in San Franscisco California on May/June 2017.
Andre Royo, who plays Timothee Chalamet's sponsor, Spencer, is perhaps best known for previously playing a drug addict himself. He starred as drug addict, Bubbles, on The Wire.
The real Nic Scheff was born July 20, 1982. In an early scene, Nic says he is 18, but he hasn't started college yet. The scene is probably around fall 2000. This explains why the characters in the movie have 90's bands on their posters and t-shirts.
The film premiered at TIFF (Toronto international Film Festival) in Canada in September 2018.
Steve Carell, Amy Ryan and Maura Tierney were all previous cast members of The Office (US).
It was revealed that Will Poulter would going to play Nic early in January, but in the official announcement, it was Timothee Chalamet who will now play the role of Nic.
Timothée Chalamet and Kaitlyn Dever previously appeared together in Men, Women & Children (2014).
Beautiful Boy had its world premiere at the Toronto International Film Festival on September 7, 2018.