"I feel ridiculously blessed. I feel so much love, honestly," the actor told the celebrity news website.
His wife said on her lifestyle blog "Old School New Rules" the baby is due to be born this winter.
The couple are already the parents of 2-year-old Olivia and 17-month-old Joshua.
People.com said the Van Der Beeks have decided to keep their new baby's gender a surprise until the child is born.
Notable deaths of 2014 [PHOTOS]
'True Detective' adds Kelly Reilly