The 42-year-old "I Do" hitmaker and "Wipeout" star announced the news of their upcoming child on Instagram along with a picture of their family of four.
"We got a new crib, now we need a new CRIB! Newest Lachey arriving 2017," the post read.
The photo which showed Vanessa's baby bump, Nick and their two kids also revealed that they are moving into another house.
The happy couple got married in 2011, and are parents to Camden John, 3, and 8-month-old daughter Brooklyn Elizabeth.