The 28-year-old paid homage to one of her heroes during her performance of "Party In The U.S.A."
"That's when the DJ dropped my favorite tune, and a Britney song was on," Cyrus sang.
"We love Britney!" she added.
Cyrus played the show outside the Raymond James Stadium in Tampa, Fla., for 7,500 vaccinated frontline workers at her "first show in about a year." Approximately 22,000 people were inside the stadium, which is a third of its normal capacity.
The Hannah Montana alum played other hits during the performance, including "Wrecking Ball," where she got emotional, as the hit is "about feeling completely broken and shattered."
"Everyone’s suffering is different, even everyone’s threshold of pain," Cyrus explained. “I wear a lot of glitter and I wear a lot of armor and I also wear my heart on my sleeve, and it gets broken a lot.”
"Thank you guys," Cyrus told the crowd when she broke down at the end of the song. "You guys would know much more about this than me, about medicine, and you know, sometimes we have to take a big spoonful of our own."
Cyrus was also joined by special guests Billy Idol and Joan Jett.
Cyrus is one of the many stars who has been lending support for Spears since the 75-minute documentary streamed on Hulu and FX. Bette Midler, Sarah Jessica Parker and Meghan McCain all tweeted "#FreeBritney" after The New York Times documentary came out.
"The Framing Britney Spears doc holy f***. No artist today would have to endure the literal torture that media/society/utter misogynists inflicted upon her. The mental health awareness conversation, culturally, could never be where it is without the awful price she has paid," Paramore singer Hayley Williams tweeted, which was retweeted by Sam Smith.
"I am praying for queen Britney!" Khloé Kardashain tweeted.
Even though Timberlake painted Spears in not the best light, the songstress is supposedly not upset with her ex. "Britney has been on the receiving end of so much hate through the years, particularly on social media. She would never want her fans to release the hounds on Justin," an insider told Us Weekly. "Hate isn’t going to solve anything, regardless of what happened in the past."
"Britney does not hold a grudge against Justin over anything he’s said or done," the source explained. "She feels that they were young and in love and both did stupid things when they were together. She was heartbroken when they separated, but it’s not something she dwells on now. She’s happy and happy for him."