The Torchwood star has landed the leading role of Julius Ashford Lily in the period drama named Gilded Lilys, according to TV Guide.
Barrowman's character is the charming son of the central family in the show, which tells the story of the opening of the first ever luxury hotel in New York City.
Blythe Danner and Sarah Bolger were announced as cast members last month.
Brian O'Byrne has also signed up to play patriarch Edwin Lily, while other cast members include Matt Lauria, Matt Long, Brigid Brannagh, Maury Sterling and Madeline Zima.
Gossip Girl writer KJ Steinberg is believed to be writing Gilded Lilys, while Rhimes and her Shondaland partner Betsy Beers are executive producers.
Rhimes is best known as the creator of Grey's Anatomy.
> 'Friday Night Lights' star Matt Lauria cast in ABC's 'Gilded Lilys'
> 'The Dark Knight' star Monique Gabriela Curnen joins ABC pilot
Watch Digital Spy's interview with John Barrowman about Torchwood below: