Comer, who plays elegant and talented killer Villanelle, beat her co-star Oh, who plays Polastri, the British spy searching for Villanelle, in the BBC America drama.
This comes after Oh was pipped to the crown by Claire Foy at last year’s award, meaning that the former Greys Anatomy star is still waiting for her first win.
It is Comer’s second major award of the year – after scoring the BAFTA – and on her debut Emmy nomination.
In addition to beating Oh, who was widely considered the favorite in the category, Comer beat Game of Thrones’ Emilia Clarke, Ozark’s Laura Linney, House of Cards’ Robin Wright, This Is Us’ Mandy Moore and How To Get Away With Murder’s Viola Davis.
Comer paid tribute to Phoebe Waller-Bridge, who created the television adaptation of Luke Jennings’ novellas, as well as Oh. “I feel so lucky to have shared it with you [Sandra],” she said.
She added that she hadn’t invited her mum and dad, who are back in Liverpool, as she “she didn’t think it’d be my time”. It seems she was wrong.
The drama is produced by UK production company Sid Gentle Films.