The 2009 IMSA Cooper Tires Atlantic Championship season was the thirty-sixth Atlantic Championship season. It was the first full season of the Championship under the sanctioning of the International Motor Sports Association. After a three-way title battle into the final round at Mazda Raceway Laguna Seca, John Edwards became the series' youngest champion, beating Jonathan Summerton on a tie-breaker, after both drivers finished on 182 points. They also finished tied on four victories, but Edwards broke the tie with four second-place finishes compared to Summerton's three.