Alba and Cash Warren, who married in 2008, are also the parents of 3-year-old Honor Marie.
UsMagazine.com said their new baby's name is Haven Garner Warren.
"She was born on Saturday, weighed 7 lbs and was 19 inches long. Healthy and happy!" Alba wrote on Facebook. "Big sister Honor couldn't be more excited about the new addition to our family. Thank you for all of your support during my pregnancy. It means the world to me."
Alba's film credits include "Spy Kids 4," "Little Fockers," "Sin City" and "Fantastic Four."