David Bradley is one of eleven actors who have had roles in both the Harry Potter and Game of Thrones franchises. Bradley played the surly caretaker Argus Filch in the Harry Potter films and the surly Lord Walder Frey in Game of Thrones. 

Other actors who crossed over include Jim Broadbent, who played Professor Horace Slughorn in Harry Potter and Archmaester Ebrose in Game of Thrones. Michelle Fairley, known for her role as Catelyn Stark in Game of Thrones, made a brief appearance as Hermione's mother in a Harry Potter movie. Natalia Tena played Osha in Game of Thrones and also had roles in the Harry Potter series.

Ralph Ineson portrayed Dagmer Cleftjaw in Game of Thrones and played Amycus Carrow in Harry Potter. Ciarán Hinds played Aberforth Dumbledore in the Harry Potter series before joining Game of Thrones as Mance Rayder. Freddie Stroma played Cormac McLaggen in Harry Potter and Dickon Tarly in Game of Thrones. Julian Glover voiced the Acromantula Aragog in Harry Potter and played Grand Maester Pycelle in Game of Thrones. 

Bronson Webb appeared as a Slytherin student in Harry Potter and had a small role in Game of Thrones. Nicholas Blane played Bob in Harry Potter and the Spice King in Game of Thrones. Rhys Ifans portrayed Xenophillius Lovegood in Harry Potter and Otto Hightower in House of the Dragon, a Game of Thrones spin-off series.