"It's my third opportunity to work with Paul," Howard added, calling the performer - who he previously worked with on 2001's A Beautiful Mind and 2006's The Da Vinci Code - "a blast & so talented."
Bettany, the husband of actress Jennifer Connelly, tweeted in response, "It's a dream come true."
The actor has had a busy year, appearing in the TV crime drama Manhunt: Unabomber as the notorious Ted Kaczynski, as well as reprising the role of Vision for next year's Avengers: Infinity War.
The announcement came on Force Friday, a third-annual event in which new items from the franchise's famed toy line go on sale at retail for the next installment in the series, Star Wars: The Last Jedi.
Howard previously revealed via social media that actors Warwick Davis and Clint Howard (his brother and a regular in his films) would be joining the cast.
It comes a few weeks after actor Michael K Williams' part was slashed from the film after he was unable to re-shoot with Howard after filming his initial scenes with Phil Lord and Christopher Miller, the directing team Howard replaced in June amid the pair's differences with LucasFilm.
Williams, who's currently filming The Red Sea Diving Resort, told Deadline, "I felt great about what I created with the directors that I worked with. It is what it is. He seemed optimistic about reprising the role he had in a future film.
"I don't think that me not being in the Star Wars family is final," he said. "I left with a very good taste in my mouth about the whole family, and I hope that I left a good taste in their mouth. They're a great group of people, the Lucas family."
The film is slated to hit theatres on May 25, 2018.
