Jaeden Martell plays Bill Denbrough, the older brother who refuses to accept that his younger brother Georgie is dead and keeps searching for him through the following summer. The Hollywood Reporter named him in June 2016 as St. Vincent actor Jaeden Lieberher, the surname he worked under early in his career, and Variety was crediting him as Jaeden Martell by 2019, the name TMDB now uses for this film.
Jeremy Ray Taylor plays Ben Hanscom, one of the outcasts who joins Bill Denbrough and his friends after being targeted by Henry Bowers and his gang. He was among the six young actors The Hollywood Reporter listed in June 2016. Taylor later told TheWrap that the young cast first saw Pennywise together in the projector scene, and that the shot "got our real reactions."
Sophia Lillis plays Beverly Marsh, the only girl in the Losers Club and a target of Henry Bowers and his gang, with Stephen Bogaert credited as Mr. Marsh. Deadline reported her casting in June 2016, after The Hollywood Reporter had listed the six boys on June 2, and in the same month that principal photography began in the Toronto area.
Finn Wolfhard plays Richie Tozier, the wisecracking friend who joins Bill Denbrough in the search for Georgie alongside Eddie and Stanley. He was one of the six boys named in The Hollywood Reporter's June 2016 report on the cast, and Deadline reported in July 2018 that he would return as young Richie in It Chapter Two, where Bill Hader plays the adult version.
Chosen Jacobs plays Mike Hanlon, one of the outcasts the group meets during the summer before the seven band together as the Losers Club, with Steven Williams credited as Leroy Hanlon. The Hollywood Reporter listed Jacobs with the other young leads in June 2016, and Deadline confirmed in July 2018 that he would reprise the role for It Chapter Two.
Jack Dylan Grazer plays Eddie Kaspbrak, one of the wisecracking friends who search for Georgie with Bill Denbrough, with Molly Atkinson credited as Sonia Kaspbrak. Grazer was among the six boys The Hollywood Reporter named on June 2, 2016, when it reported Bill Skarsgård's casting, and Deadline reported in July 2018 that he would return as young Eddie for It Chapter Two.
Wyatt Oleff plays Stanley Uris, one of the three friends who join Bill Denbrough in the search for Georgie, with Ari Cohen credited as Rabbi Uris and Janet Porter as Stanley's Mother. Oleff told TheWrap that the young cast first saw Pennywise together in the projector scene, which matches producer Barbara Muschietti's account that the filmmakers kept Pennywise away from the young cast so their reactions would be real.
Bill Skarsgård plays Pennywise, the clown who drags Georgie into a storm drain and stalks the children of Derry. The Hollywood Reporter reported on June 2, 2016 that he was in final negotiations for the part after Will Poulter, set while Cary Joji Fukunaga was attached to direct, was no longer available. UPI gave his age as 25 and noted his Hemlock Grove role.
Nicholas Hamilton as Henry Bowers
Nicholas Hamilton plays Henry Bowers, the bully who leads the gang tormenting the Losers, with Stuart Hughes credited as Officer Bowers. Deadline reported his casting in June 2016. In an August 2016 Variety interview, Hamilton spoke about filming the scenes where he had to menace Jeremy Ray Taylor, and he said that he is terrified of clowns.
Jake Sim as Belch Huggins
Jake Sim plays Belch Huggins, one of the boys who follow Henry Bowers and bully the Losers through the summer. TMDB bills him tenth, directly after Nicholas Hamilton. When The Hollywood Reporter announced Owen Teague's casting in 2016, it described the Bowers gang as a group of bullies who torment the Losers Club, which is the role Sim's character shares with the others.
Logan Thompson as Victor Criss
Logan Thompson plays Victor Criss, a regular member of the Bowers gang alongside Belch Huggins and Patrick Hockstetter. TMDB credits him eleventh, in a billing order that places the four bullies directly after Pennywise and ahead of Jackson Robert Scott and the adult cast, from Stephen Bogaert as Mr. Marsh to Steven Williams as Leroy Hanlon.
Owen Teague as Patrick Hockstetter
Owen Teague plays Patrick Hockstetter, a member of the gang that follows Henry Bowers. The Hollywood Reporter announced his casting as an exclusive in 2016 and introduced him as a Bloodline actor. When Variety reported on his next project, the thriller Mary with Gary Oldman, it described Hockstetter as the psychopathic bully of the Bowers Gang.