The actor has landed a major recurring role in the show, Deadline reports.
His character Calvino is an Italian prince who becomes a suitor for Lucrezia (Holliday Grainger).
Alpay is probably best known for his role as Mark Smeaton in Showtime's former historical series The Tudors.
His other credits include guest appearances in shows including Rizzoli & Isles, Fairly Legal and Dollhouse. He recently appeared in the Fox pilot Weekends At Bellevue, but the project was not picked up.
The Borgias, which was renewed for a second season in April, is expected to return to the US next year.
The first season is currently airing in the UK on Saturdays at 9pm on Sky Atlantic.
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