"This commencement will no doubt go down as one of the most memorable and cherished events in the history of our great university," Tulane president Scott S. Cowen said.
Degrees were awarded to nearly 2,200 graduates and honorary degrees were presented to Mr. Bush, Mr. Clinton and several others.
The former presidents, who have raised nearly $130 million in relief money for victims of the Aug. 29 storm, received several standing ovations from the graduates and others at the event.
Mr. Bush and Mr. Clinton in turn saluted the courage of the school, faculty and the 88 percent of the students who returned for the spring semester and to help the city rebuild.
"The flood waters may have breached the levees that surround this city and may have destroyed home after home, block after block, but today we also know they couldn't break the spirit of the people who call this remarkable, improbable city home," Mr. Bush said.
Tulane students pitched in to help both before and after the hurricane Bush said, helping with medical operations, search and rescue efforts, and delivering drugs and medical supplies to the New Orleans Convention Center, where thousands of refugees huddled.
Mr. Clinton said Hurricane Katrina and the enormous response it provoked should teach the graduates at least one thing.
"It is a positive manifestation of the most important fact of your lives — the interdependence of human beings on this planet," Clinton said. "And if you look at the negative aspects of Katrina, the lives lost, the property washed away, dreams broken, it is also evidence of our interdependence."
Tulane used the commencement to celebrate the culture of New Orleans, handing out Mardi Gras beads with ceramic medallions embossed with the fleur de lis, the symbol of the city, and second-line handkerchiefs with the words, "Do you know what it means to miss New Orleans?" on them.
In place of an invocation, jazz historian Michael White played "Just a Closer Walk With Thee." The song was played in the tradition of a jazz funeral, slow and mournful at first, fast an upbeat to represent rebirth at the end.
"Life's like that," Mr. Clinton said. "It's always about new beginnings. I wish you many."
The ceremony closed with a surprise visit by comedian Ellen DeGeneres, who came out wearing a bathrobe.
"I heard everyone was going to be wearing robes," she said, then offered her own advice to the graduating class. "Remember to exfoliate, moisturize, exercise and floss."