After her performance, Underwood took to Twitter to share how much fun she had returning to the show that kicked off her superstardom.
"I had so much fun back on @AmericanIdol tonight! Good luck to @scarypoolparty and @TheLaineHardy and all the contestants on whatever greatness lies ahead," she wrote. "Thanks, Idol, for always welcoming me home! 💖 #AmericanIdolFinale"
Earlier this month, Underwood opened up to ET about her current Cry Pretty Tour 360, which she said is a family affair.
"Our first day of the Storyteller Tour, my son Isaiah walked for the first time," she told ET exclusively behind the scenes of her new show. "Now he's four and we're on the Cry Pretty Tour. I just know we're gonna have many more milestones with him and with Jacob, who is three months old."
Headlining a 55-city tour is a lot of work, but there's least one aspect of tour life that gets easier for this working mom.
"I don't have a house to clean," she shared. "I don't have as much laundry to do. I get to work out more consistently when I'm out on the road. I can't get up there and do what I do how I would like to do it if I'm out of shape."
Sunday's 3-hour Idol finale also included performances by season 8 runner-up Adam Lambert, current judge Luke Bryan, "This Is How We Do It" singer Montell Jordan and Daddy Yankee & Katy Perry among others.
Check out Carrie Underwood's full performance below.