The shooting on the bus near Fontaine Street and Crest Avenue was reported around 1:30 p.m., Oakland police said.
AC Transit spokesman Clarence Johnson said a male victim was shot while near the back of the bus on the 46 line.
The victim was taken to Highland Hospital with a gunshot wound to his leg.
Johnson said the injury may be have been self-inflicted.
After the gun went off, the bus driver pulled over the bus and the victim was transported.
The roughly dozen other passengers on board were picked up by another bus, Johnson said.
No other injuries were reported and the coach was not damaged in the shooting, he said.
