The 449 kilogramme (990 pound) haul was found on a dhow, a type of sailing vessel, intercepted by HMAS Darwin while patrolling the Indian Ocean some 40 nautical miles off Somalia's east coast.
The ship's commander Terry Morrison said the seizure "removed a major source of funding for terrorist and criminal networks which included Al-Qaeda, the Taliban and Al-Shabaab".
The drugs were hidden in 20 bags, each weighing between 20 to 25 kilogrammes each.
HMAS Darwin is part of Combined Maritime Forces (CMF), a naval partnership involving 30 nations that patrols 2.5 million square miles of international waters.
The bust, the CMF's seventh "significant seizure" this year, came three weeks after the Australian and British navies jointly found 1,032 kilogrammes of heroin -- their largest-ever haul -- on a dhow off the coast of east Africa near Kenya and Tanzania.
The drugs were estimated to have a street value of 289 million Australian Dollars.