Rivera was confirmed dead on July 13, days after she was reported missing following a boat ride on Lake Piru.
Riley, who has a self-titled EP out Oct. 2, sang "A Moment." Ahead of her performance, she was encouraged by Glee co-stars, including Chord Overstreet, who wrote on Twitter, "I can’t wait to see this amber!! You’re gonna crush it! Love you Amb!"
Photos of Rivera -- including some with her son, Josey -- displayed on a screen beside Riley as she powerfully belted out the ballad.
Rivera was confirmed dead on July 13, days after she was reported missing following a boat ride on Lake Piru in California with her young son, Josey. The late actress' Glee co-stars remembered her with heartbreaking posts on social media.
On July 23, Riley reflected on their time singing together on Glee, declaring they had the "best duets on the show."
"Miss you baby girl and I love you #NayaRivera," she wrote. "I’m so mad the world will never see how high you could have soared. Her brain was brilliant. She was smart and as quick as a whip. Always had me in stitches, we would be in tears laughing so hard at one another."
"I say your name everyday and hold you in my heart, just like I do Cory [Monteith]," Riley expressed, before sharing that the former cast and crew have been coming together as a family to show love all because of her.
"Your presence brought so much excitement, so much passion, so much joy, and in your absence you’re STILL holding us accountable and getting us together," she added. "I’ve cried until my tear ducts have dried out, now it’s time to celebrate the fact that us mere humans got to experience walking through life with an earth angel. Rest well. I pray you found the peace we all are searching for."
See more on Rivera in the video below.