The rapper, who has recently been working with Damian Marley, revealed the sex of the baby on his hip-hop blog.
"Personally, life is good. I'm sure that y'all heard [Kelis] is expecting. The internet seems to be more excited than I am. It's crazy!" he wrote.
"I got too much to think about, and I didn't wanna leave all my fans out the loop. But I wanted to let ya'll know from me personally that I'm having my first SON!!!!!"
The couple married in Atlanta in 2005 after a two-year relationship.