Dubia and Madagascar hissing cockroaches were among the haul seized from a commercial breeder at Bathurst, in central western NSW.
The exotic cockroaches, which are illegal to import, keep, breed or sell in Australia, have an estimated value of up to $200,000.
According to the Department of Climate Change, Energy, the Environment and Water (DCCEEW), this makes it Australia's largest-ever illegal exotic invertebrate seizure.
"We take our job protecting Australia's unique biodiversity and breaches of national environment law very seriously," a department spokesperson said."We're seeing illegal breeding and trading of exotic cockroaches and we're putting pet businesses and pet owners on notice."
Images shared by the department show the critters lining the length of a crate and a single cockroach almost the size of a palm.
Authorities fear exotic cockroaches, which have not been subject to environmental risk assessments, may spread disease and harm native wildlife and agriculture.
Invasive Species Council policy director Carol Booth said the discovery was shocking and raised questions about the scale of Australia's illegal exotic wildlife market.
"Unfortunately, there is a growing global trend in keeping exotic invertebrates as pets, including invasive ant species," Dr Booth said in a statement.
"Biosecurity authorities should pay close attention to this emerging new pathway.
"Given the risks to our native wildlife, these crimes deserve severe penalties, but most such crimes attract only low penalties."
Offenders will be penalised, the DCCEEW spokesperson said.
Only species on the live import list can be legally imported into Australia.
"If you are found to possess, breed or trade exotic cockroaches such as Dubia cockroaches and Madagascar hissing cockroaches, they will be seized and you could face penalties under federal law," the spokesperson said.
"Reptile owners who have been using Dubia roaches as feeders are encouraged to seek legal alternatives such as crickets and wood roaches."
The seized cockroaches will be euthanised and disposed of by the NSW primary industries department.
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