Ian confirmed to People on Monday (October 29) that Erin is pregnant with the couple's second child.
"I feel blessed, having a family is something that I've always wanted. Having a second child is the realisation of a dream come true," the actor explained.
Ian and Erin's baby is due in May 2013.
The Zierings are already parents to daughter Mia Loren, who was born 18 months ago.
Erin and Ian married in 2010 at a private ceremony in Newport Beach, California.
Ian was previously married to model-actress Nikki Ziering from 1997 to 2002.