The couple welcomed their second child, daughter Quinn Sophie, on Friday, his rep told ABC News.
The baby was born in Los Angeles at 12:39 p.m.. She weighed 7 lbs., 9 oz. and is 22 in. long.
“Our second miracle has arrived and she is perfect," the couple told ABC News in a statement.
This is the second child for the actor and his wife, who have a 2-year-old son named Jax.
"I love being a dad so much I'm going to do it one more time tomorrow," Arnold tweeted on Thursday evening.