The koala climbed a metal pole on a traffic island after narrowly avoiding being hit by a car.
Worried it might fall into oncoming traffic, the bus driver retrieved the koala and brought it aboard before calling wildlife rescue.
Viral footage shows Peri sitting alone on the bus, perched atop a divider screen with his hands and feet clinging to a pole.
Peri was taken to the RSPCA for a check-up and later given the all-clear.
ABC reported the bus driver was also uninjured, having acted cautiously by wrapping the koala in a jacket before bringing him aboard.
Peri was released into the nearby Seven Hills Bushland Reserve the next day.
Video of the release shows Peri scrambling quickly up a tree and along a long branch.
Brisbane Lord Mayor Adrian Schrinner said he often refers to Brisbane as “the most Australian place on earth”, and said a koala on a bus proved his point.
“Every day our bus drivers do an incredible job keeping Brisbane moving, but this driver really did go above and beyond to keep this koala out of harm’s way,” Schrinner said in a statement to the ABC.
Koalas are approaching the end of their mating season, a time when they are more active as they search for partners.
Barkla told the ABC koalas are “delicate creatures, but they also can be quite ferocious … with their claws”.
“We recommend keeping your distance and just let us handle the rescue.”
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