Rachel McAdams on Why She's Excited for Her Son to See 'Are You There God? It's Me, Margaret' (Exclusive)

The celebrated actress spoke with ET at the LA premiere for her new film, based on the iconic Judy Blume novel, on Sunday.

Rachel McAdams is looking forward to sharing her new film with her kids as she stars in the film adaptation of Judy Blume's iconic 1970 coming-of-age novel, Are You There God? It's Me, Margaret.

ET's Cassie DiLaura spoke with McAdams at the Los Angeles premiere of her new movie, in which she plays Barbara Simon, mother to the film's titular Margaret Simon (played by Abby Ryder Fortson).

Reflecting on showing the film -- which candidly and honestly details a young girl's spiritual quest and her efforts to navigate puberty, emotional maturity and deep philosophical questions -- McAdams said of showing the film to her young daughter sometime in the future, "I just hope she's not embarrassed."

McAdams and her partner, Jamie Linden -- who are famously private about their personal lives -- share a 5-year-old son and a daughter they welcomed sometime in late 2020 or early 2021.

"She probably will be [embarrassed], so I'm just gonna prepare myself for that," McAdams added with a laugh. "But I'm really excited to show it to my son too!"

"I feel like it's great for guys to see behind the scenes... to just normalize what's really normal and create compassion between the sexes," McAdams added. "So I hope a lot of boys will go and see this with their moms, or their dads too."

As for reflecting on her own childhood while starring in the coming-of-age story, McAdams joked that there was "a little PTSD there, yeah, I'm not gonna lie. But, you know, it's a beautiful time as well."

"I love the passion that goes into every little thing. It's like, 'I might die if I don't get my period by then!' and I think Judy just hit the nail on the head with that. She really got inside the mind of a youngster," McAdams said.

Bringing the titular Margaret to life on the big screen is Fortson, who McAdams had nothing but praise for. ET was with the 15-year-old actress at her home, with her mom, ahead of Sunday's premiere, and they both expressed their gratitude for the care and consideration McAdams had for Fortson -- as her co-star and on-screen mom.

"That means a lot," McAdams said. "It's a tough business, no matter what age you are, you know? You gotta watch each other's back. She has a great family that takes care of her and she's such an old soul, you know? I mean, she's far more mature than I am."

Are You There God? It's Me, Margaret comes out in theaters Apr. 28.