Following weeks of speculation, the leading Dodge team in NASCAR's top series has confirmed that the 25-year-old will drive the #12 car from next year.
Keselowski will also race for the championship in the Nationwide Series in 2010.
"We are very excited to welcome Brad to the Penske Racing family," said Roger Penske. "Brad has shown terrific success on track the past several years and has quickly established himself as one of the top young stars in racing.
"He comes from an impressive family background in motorsports. He is a proven winner and a welcome addition to our team."
Keselowski's deal will bring to and end his period at Hendrick Motorsports and Dale Earnahrdt's Jr team at least for the time being.
Earlier this month he had suggested that if he were to drive for Earnhardt's team in the Nationwide Series, he would have to drive a Chevy in Cup as well, but Penske's offer allows him to have a further go at the title in the second tier series, while competing for one of the best organizations in Cup.
"Penske Racing is one of the top teams in all of motorsports and I am honored to join Roger Penske's organization and compete for wins with his Cup and Nationwide Series teams," Keselowski said.
"This is a great opportunity for me to continue competing in the Nationwide Series and to run my first full season in the Cup Series with a strong and experienced team."
In just his fifth Sprint Cup start this year, while running a limited schedule, Keselowski scored his first win in the series in a controversial finish at Talladega, driving for low-budget team Phoenix Racing.
In a total eight starts this season, he has scored three top-10 finishes, one of them while racing a fifth car for Hendrick Motorsports at Darlington.
Penske Racing's Kurt Busch is currently the best Dodge driver in the standing and this weekend at Atlanta he could secure a place in the Chase for championship.
Keselowski tight lipped on Penske linkXisco heads back to Spain
