Most of the main second-season cast will be returning for season three. Luke Newton and Nicola Coughlan will take the lead as Colin and Penelope, respectively. The rest of the cast includes Ruth Gemmell (Violet), Luke Thompson (Benedict), Claudia Jessie (Eloise), Golda Rosheuvel (Queen Charlotte), and Adjoa Andoh (Lady Danbury). Jonathan Bailey (Anthony) and Simone Ashley (Kate) are also returning. Famously, season one leading man Regé-Jean Page (Simon) departed the series after just one season, and Phoebe Dynevor (Daphne) has also shared she won't be returning for season three.
Another season two cast member who's not returning is Charithra Chandran, who plays Edwina Sharma. She told Indian Express in August 2022 that she was not on set for the third season.
Ahead of the beginning of filming for season three, Netflix announced that the role of Francesca, previously played by Ruby Stokes, will now be played by Hannah Dodd. On 20 July, the streamer announced a trio of new characters: Daniel Francis will play Marcus Anderson, Sam Phillips will play Lord Debling, and James Phoon will play Harry Dankworth.
Another new face joining the season three cast is Hannah New, best known as the leading lady of "Black Sails." According to Deadline, the actor will portray Lady Tilley Arnold, a firebrand widow who "enjoys the privileges and power that come with being at the helm of her former husband's estate, living life on her own terms with financial independence and sexual freedom."