The discovery was made by Helen Ranson during a spider spotting nature expedition on the New South Wales South Coast last year.
Canberra's spider man Stuart Harris led the BioBlitz expedition in the Murrah Flora Reserve for a group who were interested in finding spiders.
Stuart Harris, Julie Morgan, Helen Ransom and Diane Deans on the BioBlitz expedition.
"She said to me 'oh Stuart, what's this?' and I looked at it and was like 'oh no, that's a new species', I just knew straight away," Harris said.
"We were all over the moon jumping around, you can imagine how they felt.
"They just went out for a day in the bush to maybe find some pretty spiders and then they found a new species."
The spider, which on Wednesday was named Maratus sapphirus, was sent to Dr Jurgen Otto, a peacock spider expert who confirmed Harris' suspicions.
Harris said the name Maratus sapphirus came from his suggestion of sapphire.
"Maratus which means peacock spider is the name that's given to any spider in that genus [type]," he said.
Harris said the chances of finding a new species as a citizen scientist was slim, saying the find was "significant" not only for the finders but to experts.