He says America is "by almost every measure" better now. Obama also says the country "also happens to be better off than when I took office, but that's a longer story."
That line drew cheers and applause from the audience at the historically black college in the nation's capital. Obama then said "that's a different discussion for another speech."
The 54-year-old president tells graduates that most of them were just starting high school when he was first elected to the White House.
He says: "I used to joke about being old. Now I realize I'm old. It's not a joke anymore."