Hathaway, 35, and Moore, 34, reminisced about the 2001 movie and agreed to get together during an exchange Thursday on Instagram.
Moore shared a throwback photo of herself and Hathaway attending the Los Angeles premiere of The Princess Diaries. Hathaway wore a strapless dress, while Moore sported a denim jacket and jeans.
"I guess this film came out just over 17 years ago??" Moore captioned the post. "@annehathaway was already a movie star and I showed up to my first premiere in a casual denim suit. Hey, it was 2001! #tbt #theprincessdiaries."
Hathaway responded to Moore in the comments.
"That's the face I make when I'm trying to not flop sweat on a terrifically famous pop star," the actress wrote. "So happy for all that you have going on!"
Hathaway and Moore also joked about a scene in The Princess Diaries where Hathaway's character, Mia Thermopolis, plasters Moore's character, Lana Thomas, with ice cream.
"Let's get together and throw ice cream at each other soon," Hathaway said.
"Hello friend! Count me in. It'd be an honor to be coned by you again!" Moore replied.
The Princess Diaries opened in theaters in August 2001, and was followed by the sequel The Princess Diaries 2: Royal Engagement in 2004. Hathaway paid tribute to the film and its late director, Garry Marshall, on the movie's 15th anniversary in 2016.
"To all the fans who have loved Mia, Louie, Lily, Joe, Michael and, of course, Queen Clarisse, thank you from the bottom of my heart!" the star wrote.
"And to Garry Marshall, thank you for making me a princess. I love you always my beloved friend and teacher, and I miss you every day xx," she added.