"Our baby boy is here," El Moussa wrote in the caption, adding that he was born on Tuesday. "Mama & baby are happy, healthy, tired but doing well. Our hearts are so happy."
The "Flip or Flop" and "Selling Sunset" stars received plenty of well-wishes over the announcement, including HGTV’s account, which commented: "Welcome to the HGTV family little one!"
TAREK EL MOUSSA DITCHES ‘LONELY HOLIDAYS’ THANKS TO WIFE HEATHER: ‘NEVER GOING BACK’
Tarek El Moussa and Heather Rae Young announced their pregnancy last summer. (Axelle/Bauer-Griffin / FilmMagic / File)
The El Moussas, who were married in 2021, announced their pregnancy last summer. El Moussa already shares Taylor, 12, and Brayden, 7, with ex-wife Christina Hall.
The couple told People magazine they were happily surprised last year when they conceived naturally while in the middle of IVF treatments.
"It was a huge shock," Young told the magazine. "We just weren't expecting this. We had just gone through IVF. We had embryos on ice. We had a plan. I think when you least expect it and there's no stress in your life, the world just brought us what was meant to be. I'm so excited that it happened like this."
Young calls herself a "bonus mom" to her stepchildren.
"I'm just obsessed with my kids," El Moussa told People last year. "They're my everything, so having another one is just icing on the cake. I'm so excited."