Northern Ireland winger McCourt had a year left on his previous deal.
And, asked if he had been tempted to leave Celtic, he said: "I wouldn't say tempted. When you're not playing as much football as you like then you obviously have to consider your options.
"But after a few chats with the manager, I wasn't long making my mind up to stay here.
"It's a club I love and I'd have been disappointed to leave after the two years I've had here.
"I want to be successful here and I want my time here to be filled with medals; I haven't got one yet."
McCourt played 14 times under previous boss Tony Mowbray, scoring three goals including two superb solo efforts.
He was an unused substitute as Celtic lost 3-0 to Sporting Braga in the first leg of the Champions League third qualifying round.
Bookmark with:
What are these?