The pair – who costar on Disney's Liv and Maddie, as well as perform together in musical duo The Girl and the Dreamcatcher – attended the Los Angeles ceremony together on Sunday, posing side-by-side before presenting onstage.
Cameron, 20, popped in a pink crop top and white circle skirt, while McCartan, 22, kept it casual in a printed button down and gray jacket.
On the big night, Cameron took to Twitter, writing, "I am SO HAPPY I COULD BREAK TO PIECES."
I am SO HAPPY I COULD BREAK TO PIECES— Dove Cameron (@DoveCameron) April 30, 2016
VIDEO: Kelsea Ballerini, Mark Cuban and Jiff the Pomeranian Hit the Radio Disney Music Awards Red Carpet
The RDMAs marked Cameron and McCartan's first red carpet event since getting engaged earlier this month.
Cameron previously told PEOPLE that her fiancé's proposal was "very spur-of-the moment" yet "perfect."
Of the big moment, Cameron only revealed that "it was more romantic and bohemian than traditional."
"Because we already knew we wanted to get married one day, I didn't expect it to change anything," Cameron told PEOPLE of changing her relationship status. "But 'fiancé' and 'boyfriend and girlfriend' is worlds apart. I literally feel like I've never been so calm before. I feel rooted to the ground. I feel good."
As for wedding planning, McCartan told PEOPLE recently: "We want to do it right, and planning a wedding is no small feat, and we don't want it to be something that we have to squeeze in between jobs, so we're going to wait until the right moment."
He added, "We're going to do it right, and we're going to do it the way we want to and take our time – we have plenty."