It happened Wednesday at Joint Base Myer-Henderson in Arlington, Virginia.
President Obama was honored for eight years as Commander in Chief at the ceremony.
He expressed gratitude to the troops and their families who attended the ceremony.
"A lot of Americans don't see the sacrifices you make on our behalf," Obama said. "But as commander-in-chief I do. I've been humbled by you consistently."
It's unclear what caused the man to pass out.