"We are so excited to announce the birth of the newest member of the McDermott family! Please join us in welcoming Beau Dean McDermott," Spelling, 43, tweeted Thursday.
Spelling and McDermott are already parents to Finn, 4; Hattie, 5; Stella, 8; and Liam, 9. McDermott, 50, also has a son Jack, 18, from his previous marriage.
The actors-turned-reality stars' fifth child comes after a tumultuous few years in the couple's marriage. In 2013, it was revealed that McDermott cheated on Spelling, a revelation that was explored on their Lifetime show True Tori.
And so when they discovered Spelling were pregnant last year, it was an unexpected blessing. "It was a total surprise," Spelling said at the time. "But we always wanted a big family. I'm really excited."