O’Brien worked alongside Fenlon at Bohemians and was spotted alongside the new Hibernian manager on Saturday during the club’s 3-1 defeat away to St.Johnstone.
Hibs manager Pat Fenlon said: “I’m delighted to be able to put such a strong management team together. Billy possesses an incredible knowledge of the Scottish game and the strengths that Liam brings will be extremely valuable to the Club.
“We all share a huge passion for the game and a desire to create a winning culture here at Hibernian.”
