The twins, who were named Darby Galen and Sullivan Patrick, were born in Los Angeles and join the Dempseys' four-year-old daughter, Tallulah, in the growing household.
Dempsey, 41, who has won the hearts of millions as Dr. Derek "McDreamy" Shepherd on Grey's Anatomy, announced the pregnancy in September on Live with Regis and Kelly. Since then, he's talked at length about how he puts family first and keeps priorities in line.
In January, he posed for Life with his head resting on Jillian's pregnant belly, reflecting on fatherhood and how it's changed him.
"Now, making money is about providing for my children," he said. "And being a father makes you look at yourself. You look at your marriage and go, 'How do I improve this? How do I keep growing and create a stable environment for my children?'"
Patrick met Jillian - a celebrity stylist who now has her own high-end cosmetics line - in 1994 when he came into her salon for a haircut. They married in 1999 at the Dempsey family farmhouse in Maine.
Congratulations to the happy family!