"We are overjoyed and feel like the luckiest parents in the world," read a statement on Duff's website. "He is surrounded by so much love!! Mom and baby are both doing extremely well."
Luca, who was born on Tuesday evening, weighed in at seven pounds and six ounces.
Duff and Comrie began dating in 2007, and were married three years later. Luca is their first child.