The Hollywood stars will join forces to present onstage at the event which is being held at the Shrine Auditorium & Expo Hall in Los Angeles and airing on Netflix.
The reunion comes 18 years after the trio starred in the classic 2006 comedy drama which follows new graduate Andrea, played by Hathaway, who lands a job as an assistant to Miranda Priestly, the demanding editor-in-chief of a high fashion magazine, portrayed by Streep.
Blunt plays Priestly's long-term assistant Emily, who gets jealous of Andrea when she starts to get more responsibilities.
Streep's performance earned her SAG and Oscar nominations for best actress.
Streaming giant Netflix announced the news on Thursday by sharing pictures of the trio as well as one of Priestly looking disparagingly over her sunglasses.
"Don't be ridiculous, Andrea. Everybody wants a Devil Wears Prada reunion...," was written alongside the post.
Blunt is nominated for a SAG award for outstanding performance by a female actor in a supporting role for her role in Christopher Nolan's epic biopic Oppenheimer.
The film's whole cast is also nominated for outstanding performance by a cast in a motion picture.
Only Murders In The Building, which sees Streep star with Steve Martin, Selena Gomez and Martin Short, is nominated for outstanding performance by an ensemble in a comedy series.
It was previously announced that Luther star Idris Elba will open the SAG Awards ceremony.
Also among the presenters lined up for the night are Oppenheimer star Cillian Murphy and his co-star, US actor Robert Downey Jr.
Friends actress Jennifer Aniston, a long-time Barbra Streisand fan, will present the life achievement award to the musical star, writer and director, known for Funny Girl, Yentl and A Star Is Born.
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