Following a meeting at Obama's transition office in downtown Chicago, the two issued a statement, pledging to "launch a new era of reform where we take on government waste and bitter partisanship in Washington.
"We hope to work together in the days and months ahead on critical challenges like solving our financial crisis, creating a new energy economy, and protecting our nation's security," they said.
Sen. Lindsey Graham, R-S.C., a McCain ally, and Rep. Rahm Emanuel, D-Ill., Obama's incoming chief of staff, also were at the meeting.
McCain, who represents Arizona, will return to the Senate where in the past he has shown a willingness to work with Democrats.
Graham said the meeting had no set agenda. McCain wanted to learn how Obama plans to proceed and "where we can fit in," Graham said, noting that legislation dealing with climate change is a potential area of common ground.
Obama transition spokeswoman Stephanie Cutter said both men think "Americans want and deserve a more effective and efficient government" and want to discuss how they can work together "to make that a reality," USA Today reported.
Last week, Obama met with Democratic primary rivals Sen. Hillary Clinton of New York and New Mexico Gov. Bill Richardson, both said to be under consideration for the secretary of state position. Obama tapped primary rival Sen. Joe Biden of Delaware as his vice president.