The former England youth international began his career at the Manchester City Academy before joining Leicester City.
He was released by the Foxes last month and subsequently spent time with Motherwell at their pre-season training camp in the Netherlands.
Kennedy told the club’s official website: “I’ve been here for over a week after being with the team over in the Netherlands and I’ve been really impressed with the facilities and the club itself.
“I’ve had such a good time at both Manchester City and Leicester, both great clubs, but I’ve been lucky enough to get the move up to Scotland and I can’t wait to get started.
“I think I have played enough football at Development Level and it’s time to make that step up. If I am training well and working hard, hopefully I get a chance but I know I’ll need to be patient.”