The shipment included 3,810 pounds of methamphetamine, along with 56 pounds of cocaine and 11.5 pounds of heroin, federal authorities said.
Officers with U.S. Customs and Border Protection seized three shipping containers containing the drugs on Jan. 11 at the Los Angeles/Long Beach seaport.
Following an investigation, federal authorities in Australia this week arrested two U.S. citizens and four Australian citizens.
Federal officials say the seizure dealt a significant blow to the drug trafficking organization behind the shipments.
"Along with our law enforcement partners here and around the world, we continue in a day-to-day battle against the blight of methamphetamine that continues to devastate our communities," said Joseph Macias, Special Agent-In-Charge for Homeland Security Investigations Los Angeles. "Through a collaborative effort -- pooling our information, resources and expertise - we are keeping this dangerous contraband from reaching our streets and potentially saving lives."