The Hollywood couple, who got married in October 2013, announced the birth of their son together on Thursday, April 14.
"Our little baby boy has arrived!!" Clarkson, 33, tweeted. "Remington Alexander Blackstock was born 4/12/16 & he is healthy & we couldn't be happier or more in love!"
In August, the 'American Idol' alum revealed that she was expecting her second child. The "Heartbeat Song" singer became so emotional during a performance at L.A.'s Staples Center that she blurted out the baby news onstage.
"I was not planning on announcing this but I'm totally pregnant," she said at the time. "I didn't want you to think I was on pills or something! Everything is great. I haven't vomited yet, that's a win!"
In her interview with CBS This Morning in November, Clarkson spoke up about her tough second pregnancy. "I'm familiar with all-day sickness," she said. "I have to get IVs and fluids because I get so dehydrated. It's really bad."
Clarkson and Blackstock, 39, already share a daughter River Rose who was born in June 2014 but Blackstock is also a father to daughter Savannah, 14, and son Seth, 8, from a previous relationship.
Watch Kelly Clarkson in her classic "Because Of You" video below: