Cheney, who has been virtually absent from the 2008 campaign trail, offered his endorsement at an appearance in Laramie, Wyo.
"I believe the right leader for this moment in history is Sen. John McCain," said Cheney, who grew up in Wyoming and represented the state in the U.S. House of Representatives. "John is a man who understands the danger facing America. He's a man who has looked into the face of evil and not flinched."
Cheney also said he was pleased McCain has "chosen a running mate with executive talent, toughness and common sense, our next vice president, Sarah Palin."
At an appearance Saturday in Pueblo, Colo., Obama used the Cheney endorsement to underscore his charge that McCain represents a continuation of current policies in Washington.
"I'd like to congratulate Senator McCain on this endorsement because he really earned it," Obama said. "That endorsement didn't come easy. Senator McCain had to vote 90 percent of the time with George Bush and Dick Cheney to get it."