HBO has announced that Warwick Davis, who is known for his role as Professor Filtwick in the Harry Potter film series, will reprise his role for HBO's Harry Potter. Davis also has an additional credit in the films for portraying Griphook, the goblin from Gringotts bank.

Additionally, the studio also announced that several other characters have been cast. Elijah Oshin will portray Dean Thomas, Finn Stephens will essay Vincent Crabbe, and William Nash will play Gregory Goyle. Hogwarts professors who are cast are Sirine Saba as Professor Pomona Sprout, Richard Durden as Professor Cuthbert Binns, and Brid Brennan as Madam Poppy Pomfrey. Leigh Gill will portray Griphook in the series. Gill is known for his role in Joker (2019).

Touted as a faithful adaptation of the books, the series will also star Dominic McLaughlin as Harry Potter, Arabella Stanton as Hermione Granger, and Alastair Stout as Ron Weasley. The rest of the cast includes John Lithgow, Janet McTeer, Nick Frost, Paapa Essiedu, Bertie Carvel, Anton Lesser, Paul Whitehouse, Johnny Flynn, and Bel Powley, amongst others.

Filming is currently underway for the series, which is written by Francesca Gardiner, with Mark Mylod serving as a director. Gardiner and Mylod serve as executive producer with author JK Rowling, Neil Blair, David Heyman, and Ruth Kenley-Letts. Bronte Film, Heyday Films, and Warner Bros Television are backing the series, which is set to premiere in 2027.