Some 116 different kinds of illegally imported products - together weighing 38 tonnes - were confiscated during a raid on a warehouse in Sydney.
Australia has some of the strictest biosecurity rules in the world.
Penalties for breaching them include jail time and fines of up to A$6.8 million ($4.5m; £3.7m).
Authorities searched the warehouse after border officials noticed a suspicious package in February.
Describing the scale of find as "shocking", Agriculture Minister Murray Watt said it had been one of Australia's largest biosecurity detections in a statement.
"We often see smaller quantities of risk products brought in through parcels in the mail or carried by incoming passengers... However, a discovery of this size and nature is a stark reminder of what's at stake if we don't continue to fiercely protect our precious biosecurity."
Australia is one of the few countries in the world to remain free from some of the world's most invasive pests and diseases, like foot-and-mouth disease and avian influenza H5N1.
Officials confiscated seven shipping containers' worth of goods which "could have posed an unacceptable risk" of introducing such diseases and pests, Australia's Director of Biosecurity Andrew Metcalfe said.