The actor, 31, and his wife Sheila Hafsadi welcomed their second child, a baby girl, on May 31, he announced on social media.
Daughter Presley Bowie Rathbone weighed in at 8 lbs, 2 oz.
"Today!! Our daughter is born!! Welcomed into the world at 8:38 am with love & joy," Rathbone tweeted along with a photo of the proud parents moments after their newborn's arrival.
In March, Rathbone announced there was another baby on the way when he posted a black-and-white throwback photo of his wife during her first pregnancy on Instagram.