Son River James Murray was born on April 22 in Los Angeles, weighing in at 7 lbs., 11 oz.
Murray, who plays special agent Timothy McGee on the CBS crime drama, and his wife also have a daughter, Caitlyn.
"Carrie and I are pretty Zen'd out right now," the 32-year-old actor told People. "[But we know] our 3-year-old will bring us back to reality soon enough!"
Murray and his wife, a teacher, have been married since 2005.