The 28-year-old actress proudly showed off her growing baby bump on Instagram. It will be her first child with the 32-year-old retired tennis player, reported Ace Showbiz.
"So this happened... #the3ofus," the mother-to-be announces it online.
A representative for the Sports Illustrated Swimsuit model also confirmed the pregnancy news, "I'm happy to confirm Brooklyn and Andy are expecting a new addition to their family in the autumn of this year."
Decker married Roddick, who now works for Fox Sports, in 2009 after a year of engagement.