The star looked incredible for the performance, wearing a high-slit black dress which she accessorised with matching over the knee leather boots.
The 54-year-old completed her look with a striking red lipstick and switched up her blonde hairstyle by adding red tips to it.
The three-hour star-studded American Idol finale featured many more artists, such as Ellie Goulding, Pitbull, James Blunt and TLC.
It also featured previous American Idol contestants, such as Nutsa Buzaladze, who had the privilege of performing onstage with Kylie.
Sunday's show was a historic one as it saw Iam Tongi win the popular show at just 18 years old.
Iam, who was mentored by Keith Urban on the show, was crowned the winner after beating runners-up Megan Danielle and Colin Stough.
The singer, who was born in Hawaii but is of Tongan and Samoan heritage, performed several songs during the night, including "Monsters" and his single "I'll Be Seeing You".
Iam had been a favourite with the judges and the audience since his first audition. The high-schooler performed "Monsters" and dedicated it at his father, who had passed away months before his audition.
"I was not worried about whether you were going to make it through the song, I was worried about whether we were going to make it through the song. Your daddy is very proud," said judge Lionel Richie at the time, as fellow judge Katy Perry added: "What a fantastic song to pick. You're making these grown men cry."
"I cannot handle your heart breaking about your dad because my nephew lost his dad and he came to live with me and just seeing you missing your dad sucks. Gosh man, you've got a great voice. You did everything perfectly and I love you and want to see you have fun," added Luke Bryan.
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