After scaling the wall, the primates were able to walk among the 2,500 visitors to Hanover's Experience Zoo.
While the chimps were content to taste life on the other side of the fence, a five year-old-girl and and an elderly man were hurt in the panic as staff hurriedly evacuated the park, the Daily Mail reported.
A total of 27 seven police cars raced to the scene on Wednesday to help steer the animals, which are often aggressive, extremely strong and capable of killing a human in seconds. They were joined by zookeepers armed with pepper spray.
"At first it was quiet and then panic broke out," a visitor said.
A five-year-old girl hurt herself when she fell over at the sight of them but was not seriously injured.
An elderly man also needed medical attention when he was locked in the tropical house in 100 degree heat as the chimps roamed outside.
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Four of the five chimps, seven in total live in the enclosure, tasted freedom and decided they didn't like it much.
They wandered back to the enclosure on their own, but leader of the pack Maxi was enjoying himself on the outside.
"He took himself off to see the head gorilla," Simone Hagenmeyer, the zoo spokeswoman said.
"He was a bit harder to coax back. He's getting on a bit so we gave him a ladder to climb back into the enclosure," she added.
An inquiry is now underway to determine what happened.
The zoo could be faced with a huge bill for the fleet of police, ambulances and fire engines that raced to the scene.