The 49-year-old actress wasn't expecting to get in the recording booth for her new film, 'Dumplin'.
The actress stepped into the recording booth at Dolly Parton's request, to sing "Push and Pull" with her co-star Danielle Macdonald, and as she told ET, it ushered out the waterworks.
"[I was so nervous] but I sang through it and then got my voice. I literally couldn't have a squeak come out, and then when we finished, I remembered, I just burst into tears," Aniston told ET's Nischelle Turner at the Dumplin' junket at the Four Seasons Beverly Hills on Tuesday.
"She did get emotional after she was done," Parton -- who crafted the soundtrack -- confirmed, calling the actress a "real pro" in the booth.
"It was terrifying and fun and all of it... it was great," Aniston recalled. "[I was] fearless, yes, or fearful, depending on how you look at it. But I had Dolly and Linda Perry there, who were just patient and wonderful."
The 49-year-old actress said the experience brought back childhood memories of singing into hairbrushes and wanting to be a rock star. "I sort of had this weird dream of a lifetime just come crashing in on me," she said. "But boy... bow to all of those guys who do that. It's quite fab. It's fantastic."
Dumplin' stars Aniston as a former beauty queen whose plus-size teenage daughter, nicknamed "Dumplin'" (Macdonald), signs up for her mom's pageant in protest. The role required the former Friends star to speak in a southern accent -- and it got a big stamp of approval from Parton.
"I love picking up on accents anyway. It's something I've always been able to do a little, and that one in particular. But I also have a fantastic dialect coach who just sort of would give me little tips here and there," Aniston explained. "[The toughest thing] is not knowing if you got it right."
"I thought she did great, and I told her that. I went to see it with her... I was really impressed and I knew she worried about it," Parton recalled. "She needed to hear it from somebody who knew, so I leaned in and said, 'Your accent is great, you did a great job,' and she said, 'Whew!' but I meant it."
Stepping into the shoes of a beauty queen came a little easier.
"Especially if you're doing award shows, it's very much like what she's talking about -- the dresses and the beauty pageants, don't you think?" Parton asked Aniston. " It's kind of similar."
"It's a performance," Aniston agreed. "[It's] a little bit of going out there and putting on your sparkly, pretty self."
Dumplin' launches on Netflix and in select theaters on Friday.