Video taken Sunday at the zoo shows a man jumping the barrier, then quickly leaving the area when the tiger begins to approach, KGO reported.
One witness said a zoo employee scolded the man.
"He jumped that fence, like the little railing, and the tiger just launched at him and he jumped back up," Sam Fayad told KGO. "I heard from somebody he said he dropped his glasses or something, but when he came back up, I didn't see nothing in his hand.
Fayad told the television station that the tiger became agitated and started pacing back and forth before approaching the fence near the barrier.
"Now that we know that happened, we can definitely take it into consideration," Erin Harrison, of the Oakland Zoo, told NBC Bay Area. "We feel our barriers are great, but we can always review that and see if there's more we can do to communicate to the public."
"The Oakland Zoo meets and exceeds safety requirements set by state, federal, and AZA accreditation standards,” the zoo said in a statement. “We hope that all of our visitors act responsibly, and don't attempt to put themselves in potentially unsafe situations."