Rachel McAdams and Abby Ryder Fortson have been cast in “Are You There God? It’s Me, Margaret,” an adaptation of Judy Blume’s beloved coming-of-age book.

Fortson will play Margaret Simon, a sixth-grade girl who is going through puberty and searches the universe for any answers she can find. McAdams is portraying Margaret’s mother, Barbara.

The movie, set up at Lionsgate, will be written and directed by Kelly Fremon Craig. It’s expected to begin production in April.

“Are You There God? It’s Me, Margaret” was first published in 1970 and remains hugely popular among young, budding readers. Blume has long been opposed to screen adaptations of her seminal work, a notable list that includes “Tales of a Fourth Grade Nothing,” “Blubber,” “Forever” and “Tiger Eyes.” However, the upcoming version of “Are You There God?” — especially the casting — comes with Blume’s blessing.

“Abby is funny and tender, strong yet vulnerable. She IS Margaret,” Blume said. “And Rachel — wow! — does it get any better? A funny, loving, sexy, real woman who is also a mom. I can’t wait to see these two playing mother and daughter. It all began with trusting Kelly and Jim and they’ve proven how much this project means to them, which means everything to me.”

Blume will serve as a producer on the film, along with Fremon Craig and James L. Brooks, whose resume boasts a range of film and TV projects like “The Mary Tyler Moore Show,” “Taxi,” “The Simpsons” and “As Good as It Gets.” Fremon Craig and Brooks previously teamed on the 2016 comedic drama “The Edge of Seventeen” with Hailee Steinfeld and Woody Harrelson.

As for casting McAdams and Fortson, Freemon Craig says “there couldn’t be a better combination to bring Judy Blume’s much-beloved characters to life on screen.”

“Abby is the kind of extraordinarily rare talent that comes along once a generation. The minute she walked in the room, she knocked us off our feet with her humor, vitality, and instantly lovable presence. We knew we’d found Margaret,” she said. “Together with Rachel McAdams’ exceptional talent for creating indelible characters that make you laugh out loud, bawl your eyes out, or both.”

Producers also include Julie Ansell, Richard Sakai and Amy Brooks. Meredith Wieck and Chelsea Kujawa are overseeing the project for the studio.

McAdams, whose prolific career includes “The Notebook,” “Mean Girls” and “Spotlight,” recently starred opposite Will Ferrell in Netflix’s comedy “Eurovision Song Contest.” Up next, she will reprise her role as Dr. Christine Palmer in Disney and Marvel’s “Doctor Strange and the Multiverse of Madness.”

Fortson, another Marvel alum, is best known for the Disney superhero adventure “Ant-Man” and its sequel “Ant-Man and the Wasp,” where she portrayed the daughter of Paul Rudd’s Scott Lang. She has also appeared in “A Dog’s Journey,” “Forever My Girl” and the Duplass brothers’ shows “Togetherness” and “Room 104.” Fortson’s next film project will be the film “Rated,” which is written and directed by her father, John Fortson.

Fortson is represented by Wendi Green at Atlas Artists and attorney Alex Kohner. McAdams is represented by WME, Magnolia, and Hirsch Wallenstein.

Entertainment Weekly first reported the news.