The Bachelor's fourth-season star first announced the exciting baby news during a Monday appearance on the Today show's "Guys Tell All" segment.
Jessica also took to Instagram on Sunday, sharing photos from the couple's gender reveal party.
One picture featured the former The Bachelor star sweetly gazing at Jessica, whose little baby bump was visible in her tight, mini, long-sleeve navy blue dress.
"Yep. We're going for it!" the blonde beauty captioned the snapshot.
Bob posted the same images on his own Instagram account on Monday, one of which shows the couple's 11-year-old dog, Phoebe, wearing a blue-flower wreath with a sign attached that reads, "It's a boy!"
Bob joked that Phoebe "is all fired up" in the caption, adding that he's "happy" and "thankful" for his family.
Bob and Jessica got engaged in October 2015 and tied the knot in November 2016 in Punta Mita, Mexico.
Bob found fame when he competed for Trista Rehn's heart on The Bachelorette's first season in 2003. After Trista got engaged to Ryan Sutter -- her now-husband -- Bob went on to star on The Bachelor's fourth edition that same year.
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Bob decided to give his final rose to mortgage broker, Estella Gardinier, but he offered her a promise ring instead of an engagement ring. The couple split shortly after the season aired on ABC.