Credit: Chelsea Lauren/Getty Stringer Photo: A.J. Buckley and Fiancée Abigail Ochse

A.J. Buckley is Justified in being proud today, since he is now a daddy!

The 35-year-old actor — known from CSI: NY, Supernatural, Disturbing Behavior, and now Justified — welcomed a baby girl on Sunday, January 19 at Cedars-Sinai Hospital in L.A.

This is the first child for A.J. and his fiancée, oncology nurse Abigail Ochse.

A.J. shared the happy news earlier today, tweeting, "greatest moment in my life happened at 136am this morning when my fiancé gave birth to our little angel Willow Phoenix Buckley #ProudDad"

Aww! Love the name.

His rep told People that Willow arrived weighing 7 pounds, 5 ounces. Abigail and baby were both said to be "doing well," which is good to hear.

A.J. currently plays Danny Crowe on the FX show Justified, and he recently filmed the movie North of Hell with Katherine Heigl, Jordana Brewster, Patrick Wilson and Kevin McKidd. He played Adam Ross on CSI: NY from 2005-2013.

A.J. announced his father-to-be news back in September, and shared a sonogram of his sweet little lady.

Congrats to the couple and their growing family! This has to be such an exciting (and probably nerve-racking) time for them. Enjoy!

Sources: People , Twitter, IMDb