The Heroes star and her husband, writer/actor Hayes MacArthur, welcomed a son called Theodore Hayes MacArthur in Los Angeles.
MacArthur's father Bruce first confirmed the happy news to the Chicago Sun-Times, saying, "I can't wait to see him and say, 'Hey, baby! What's happening?'"
The couple later released a statement to Us Weekly, calling their new baby a "perfect Christmas present".
Larter married MacArthur in Maine in August last year (09).