Katherine Waterston and Alison Sudol are also on board, with Ezra Miller in talks to join the cast as well.
Folger will play Jacob, a non-wizard type who runs into Newt Scamander (Redmayne) when he stops in New York City on his travels to find and document magical creatures.
David Yates is directing from a script by J.K. Rowling, who’s making her screenwriting debut.
Set in New York roughly seven decades before Harry Potter’s saga starts, “Fantastic Beasts” is based on the Hogwarts textbook of the same name and follows the adventures of its author, Scamander. Scamander is described as a “magizoologist,” someone who studies magical creatures.
After studio execs were underwhelmed by a first group of actors tested earlier this month, Fogler came in earlier this week and won them over to land the role that several actors were chasing.
Folger was most recently seen on the ABC drama “Secrets and Lies.” He is repped by UTA and Management 360.
The film is set to bow on November 18, 2016.
Deadline Hollywood first reported the news.