The Irish International signed for one year with the Scottish champions.
Republic of Ireland manager Stephen Kenny has praised Shane Duffy after the Brighton centre-back completed a one-year loan deal with Scottish Premiership champions Celtic.
The Irish squad are training in Sofia ahead of tomorrow night's UEFA Nations League clash with Bulgaria.
Duffy leaves Brighton after becoming their record signing when he joined the seagulls from Blackburn Rovers in 2016.
After hearing of the move, Kenny explained what makes the Derry native such a good defender: