No animals survived the incident and victims included guinea pigs, mice, rats and fish, and several varieties of tropical birds, including 29-year-old Gilbert the parrot.
Gilbert was a popular attraction among visitors and locals, known for being able to speak several words, NRK reports.
Magnus Danielsen, head of police, told the network: "The fire was too hot and fire fighters who went into the pet shop encountered a lot of smoke. All the animals are dead. There was nothing to save."
The fire is thought to have most likely started in the north part of the shop where most of the animals lived. The shop is located in Storgata, in the city centre of Lillehammer.
Fire fighters brought the fire under control around 10:30pm on Wednesday night.