In a statement released by the Obama campaign, the 75-year-old Rooney said endorsing political candidates is not something he regularly does.
"As a grandfather and a citizen of this community, I think Barack Obama's thoughtful, strategic approach is important to America," Rooney said. "When I hear how excited young people seem to be when they talk about this man, I believe he will do what is best for them, which is to inspire them to be great Americans."
The Obama campaign said the Illinois senator and Rooney met Monday after Obama spoke at a meeting of the Alliance for American Manufacturing.
Obama's Democratic rival, U.S. Sen. Hillary Rodham Clinton, also addressed the gathering in Pittsburgh on Monday.
Polls show Obama trailing Clinton in Pennsylvania ahead of the April 22 primary.
"True sports fans know that you support your team when they are the underdogs," Rooney said. "Barack Obama is the underdog here, but it is with great pride that I join his team."
Last month, former Steelers running backs Franco Harris and Jerome Bettis also endorsed Obama.
