The singer's make-up artist wife Rochelle Deanna Karidis gave birth to the couple's first child on Tuesday morning (27Nov12).
The MCLeans have called the little girl Ava Jaymes.
A.J. tells In Touch magazine, "We are all doing well and are thrilled to welcome Ava to the world."
The Backstreet's Back singer and his wife wed in December (11) and the pop star wasted no time in letting fans know he was keen to become a dad.
In a post-wedding interview, he said, "We want to start a family."
The couple announced the baby news via a YouTube.com video in April (12).