Charismatic Mr Obama - who, if elected in November, will become the US' first African American president - joined the former First Lady at her Washington home for a private visit after a day of campaigning in Virginia.
Contrary to widespread speculation, representatives for Mrs Clinton insist the talks have nothing to do with reports she's seeking the vice-presidential role. "The choice here is Senator Obama's and his alone," they say.
Meanwhile, the presidential hopeful himself has made it clear the decision as to who will run alongside him for the post of vice-president is one he won't enter into lightly.
"There's no decision I'm going to make that's going to be more important before the November election," he revealed. "I intend to do it right."