The man had been on the Bay Bridge just past the Treasure Island exit threatening to jump, as lanes were blocked by rescue crews and traffic backed up.
A witness said she saw someone climb at about 2:45 p.m. onto the ledge of the upper deck of the bridge's western span, near far right lane.
"We thought he was just going to go to the call box, and then he kept going onto the ledge," the witness said.
The San Francisco Fire Department and Oakland Fire Department responded, as well as the CHP.
The two right lanes of the bridge were blocked for hours and traffic was backed up well into the MacArthur Maze.