The mummy, found in the town of Diepholz in Lower Saxony, grabbed international headlines when it was discovered by the boy at the start of August under the floorboards of his grandparent's attic.
In a chest decorated with Egyptian designs which his grandfather had brought back from his travels in North Africa in the fifties, the mummy lay hidden in the attic for years.
But tests carried out in Hamburg revealed it to be a plastic skeleton wrapped in rags, authorities said on Wednesday.
It was initially believed to be from North Africa and around 2,000 years old.
“The mummy was unwrapped and one could see relatively quickly that its contents were not ancient,” prosecutor Lutz Gaebel said.
The case was not initially solved by a computer scan because it was sprayed with an unknown substance. Investigators saw the bones but did not realize they were plastic.
The skull however is real. Gaebel said investigators believed the it had been used for educational purposes by medical students before being put with the plastic bones. It will go away for further tests, but apart from that the case is over, he admitted.