The 43-year-old television personality - who is hosting the event - is thrilled the 'We Belong Together' hitmaker agreed to return to the stage on December 31 after a disastrous performance in 2016 that was plagued with technical difficulties.
He said: ''Here's the thing - last year wasn't as planned. We all know that. I give her tremendous credit for saying, 'I'm coming back. I'm going on the same stage at the exact same moment before the ball drops in front of tens of millions of people.'''
Whilst his co-presenter Jenny McCarthy added to Us Weekly magazine: ''It's a wow! I am really grateful that, not only did she say yes, but that we gave her the chance. It's like, how many times would we love a second chance in life? I know I need about 40 of them. So I'm honoured that she said yes, and I'm honored to be a part of a show that is doing something so nice.''
Mariah announced her performance in a joint statement from Dick Clark Productions and Mariah.
They said: ''We can all agree that last year didn't go exactly as planned and we are thrilled to move forward together to provide America with an incredible night of music and celebration on Dick Clark's New Year's Rockin' Eve with Ryan Seacrest 2018. See you in Times Square!''
Mariah previously admitted she had felt ''vilified'' after the 2016 performance, which saw her singing out of time with the music.
She said: ''I didn't obsess over the New Year's Eve thing. I mean, I was upset about the fact that people didn't understand, but it's like, I can only explain it like this to you. It's like I'm the only one that has to make five million comebacks... For me there are different rules, I don't know why. I don't know why it's not OK that I was just vilified by the situation. It's very difficult, especially the way the business is now. I truly love music and always have. It's not like ... 'Oh, here's a way to get famous.' It wasn't any of those things. It was my release, it was my everything and it still is. So I think that I'm just grateful that people still tune in.''