Blake Shelton and Adam Levine "drive each other nuts".
The 'Came Here To Forget' hitmaker has gushed about his best friend and fellow 'The Voice' coach as he joked that Adam needs his "face slapped around" at times.
Blake said: "I didn't know what the hell was going on. It was this skinny guy with a white T-shirt with the collar all stretched out. I remember turning to my manager and saying, 'I think that's Adam Levine.'
"He's one of the most loving people I've ever known. We drive each other nuts, but outside of this world, he's one of my best friends and it's because of his heart. He needs his face slapped around, but he has a huge, huge heart."
And Adam is equally thrilled to be such good friends with Blake as well as with the other past and present coaches on the talent show.
He added of their friendship: "I remember when I saw him at the meeting at NBC, I was instantly very taken by him 'cause he was definitely not your typical country artist. He was not a cookie-cutter guy, and the second we met, we were friends. All of the bulls**t that we do comes from a place of love ...
"It's so cool that we are really close. Blake and Alicia and Shakira and Usher and Pharrell. It's like holy s**t, I was able to make all these new friends I never would've made in a million years. We were brought together by this crazy show. I feel so lucky to have at least at the end of the day, beyond the show itself, to have made really good friends."
Meanwhile, newcomer coach Alicia Keys didn't think she was going to like Blake as much as she did.
She told People magazine: "I like him so much. I mean, I didn't think I was gonna not like you, but I didn't expect to like you. You're a cool guy!"