The My Name Is Earl star and wife Ceren Alkac will welcome the baby - believed to be a boy - in June, reports People.
The couple married in late 2008 after a one-year engagement.
They are already parents to a 3-year-old daughter named Casper. Lee also has an 8-year-old son, Pilot Inspektor, from his relationship with Beth Riesgraf.
In October 2011, Lee signed on to appear in the NBC sitcom Up All Night as a love interest for Maya Rudolph's character Ava.
He had previously confessed that he missed working on My Name Is Earl and wanted to return to comedy.