The actor welcomed daughter Sadie in December 2013 but kept their new arrival under wraps until last night's Golden Globe Awards 2014, where Jesse confirmed his happy news.
He told People that being a father is "amazing" and he is "loving" every second – despite being sleep-deprived!
Reports that Jesse and Aryn had become parents surfaced at the end of last week, although Jesse didn't speak out until last night.
Jesse and real estate broker Aryn married in Los Angeles in September 2012 after more than five years of dating. They met before Jesse was famous, when he was living in New York and working as a teacher.
Jesse plays Dr Avery on Grey's Anatomy.