Jelly Roll is still pinching himself after joining Eminem onstage!

Over the weekend, ET spoke with the country music superstar at the CMA Fest, where he dished about one of the “coolest” moments of his life, which was performing alongside the GRAMMY-winning rapper at the Live From Detroit: The Concert at Michigan Central. The special aired Sunday on NBC.

“When I think about coolest moments of my career, right now at the top, there has to be this thing that I got to go sing with Eminem in Detroit,” he said. “I got to sing ‘Sing for the Moment’ with him, which is a record where he sampled Steven Tyler. I mean, just what an incredible night and I got to go do it in Detroit. It was unreal.”

Jelly — whose real name is Jason Bradley DeFord — said that Eminem (whose real name is Marshall Mathers) had his team reach out for the surprise performance.

“Em reached out, his team reached out and said, ‘Would you be interested in doing this since he was already there doing the secret tribute?’ I couldn’t believe it. I thought it was a joke until I met Eminem himself.”

He added, “I thought I was being joked! I even know Eminem’s manager. He’s a friend of mine. He’s really good to me. His name is Paul and I was like, ‘Paul, don’t play.’ He was like, ‘I swear.’ And as soon as I met Eminem, it was like the coolest moment ever, man.”

Jelly Roll, 39, and Eminem, 51, took the stage for the duet that saw the country crooner singing the chorus and the hook of the rapper’s song. While in the moment, Jelly told ET he was trying to keep it cool — but couldn’t.

“I was giddy, like a child,” the “Wild Ones” singer said. “You could see it all over my performance. Just the kid in me. I thought the camera was off of me. So as soon as I get through singing, I’m like, whoa, I just let this steamroller out. It’s really cool.”

Jelly Roll also took the stage alongside Melissa Etheridge and Fantasia Barrino, belting out Bob Seger’s “Old Time Rock & Roll.”

Still, after spending time in the Motor City, Jelly Roll is back to his roots in Nashville and focused on his upcoming album.

“This has been my whole life the last 11 months,” he teased to ET. “I have been drowning in this album. I’ve never wrote more songs. I’ve never took it more serious and I’m probably gonna release more music this year than I’ve ever released in a year of my career.”