[2][6] In his early career, Melling performed in stage productions of The Provoked Wife, King John, Antigone, and Plenty.

He appeared in "The Sorcerer's Shadow", an episode of the BBC television series Merlin, playing a young warlock who intends to use magic to help him win Camelot's legendary tournament.

[6][10] Of Melling's performance, New Yorker film critic Anthony Lane wrote: [I] came away haunted by a scattering of sights and sounds—above all, by the recitations of the limbless man, which thrum with genuine yearning.

That same year, he appeared in the Netflix series drama The Queen's Gambit as Harry Beltik, a chess player, friend, and competitor of Beth's in Kentucky.

[6][10][12][13] In May 2024, it was announced that Melling would be starring alongside Alexander Skarsgard in Pillion, a romantic comedy produced by Element Pictures.