In an appearance on "Fox News Sunday," McCain said the former secretary of state's endorsement of Obama for president did not blindside him.
"I've always admired and respected General Powell. We're longtime friends. This doesn't come as a surprise," Obama said.
McCain noted he has been endorsed by four other former secretaries of state, all of whom served in Republican administrations: Henry Kissinger, James A. Baker III, Lawrence Eagleburger and Alexander Haig.
Powell, a Republican and the former chairman on the Joint Chiefs of Staff and national security adviser, made his endorsement on NBC's "Meet the Press" program.
Asked whether Powell's endorsement undercuts his campaign's argument that Obama is unprepared to lead the nation, McCain said, "I think the American people will pay close attention to our message for the future and keeping America secure."