The 32-year-old singer, who has spoken extensively about desire to become a mum, welcomed a little girl called River Rose on Thursday.
New mum Kelly announced her daughter's arrival on Twitter writing, "Our baby girl River Rose Blackstock arrived on June 12th! Thank you everyone for all of your well wishes! Brandon and I are on cloud 9!! :)".
Because of You singer Kelly, who married 38-year-old talent manager Brandon Blackstock in October 2013, made no secret about wanting to start a family with her husband.
"Everybody keeps saying, 'What do you want for Christmas?' And I'm like, 'I want to be pregnant'," she said shortly after the couple tied the knot. "I want babies, yep I do!"
Kelly didn't have to wait until Christmas, however, and she announced that she was expecting in November. Two months later Kelly and Brandon found out that their new arrival would be a girl, with the Texas-born star taking to Twitter once again to tell her fans the news.
"We just found out we're having a girl officially!" She posted. "I knew it! Only a girl could cause this much drama with all this vomiting ha!"
Kelly and her husband Brandon Blackstock
While baby River is Kelly's first child, she is also stepmother to Brandon's children from his previous marriage, Seth, six, and Savannah, 12.
"My kids love her," Brandon's ex-wife Melissa told People in October. "I couldn't ask for a better stepmother for my children."