The 21-year-old full-back has represented Northern Ireland at senior level and had a spell in League Two with Shrewsbury last season.
He told the club's official website: "I'm looking forward to the move. It will be a fresh and exciting challenge for me.
"I'm very impressed with the set-up at Fleetwood and everyone has been so friendly towards me. The club will be looking to push on from League Two and hopefully I can help them gain back-to-back promotions."
Town manager Micky Mellon added: "I am delighted to bring another international footballer to Highbury. It shows how far the football club has come.
"Conor is a player who has already proved himself and he brings a lot of potential. He is a versatile player and a very good footballer."