The drugs were found when a lorry was stopped in Templepatrick
An estimated 600kgs of herbal cannabis were seized when a lorry was stopped in Templepatrick in the early hours of Wednesday.
The drugs, with an estimated value of £10m-£12m, were discovered among a “cover load” of vegetables.
NCA and PSNI officers took part in the operation.
It is understood the vehicle had travelled through Great Britain and crossed into Northern Ireland on a ferry to Larne.
Three men, including the lorry driver, were arrested on suspicion of conspiring to import controlled drugs.
The men, aged 62, 37 and 32, are from County Tyrone, County Londonderry and County Armagh. All three remain in custody.
Two premises were also searched, one in Co Derry and one in Tyrone.
National Crime Agency Belfast Branch Commander David Cunningham said it was an “incredibly significant seizure”.
“A seizure of this size will have a huge impact on the organised crime groups involved in its importation, depriving them of commodity and, most importantly, profit,” he said.
The drugs were found among a cover load of vegetables
Detective Chief Inspector Brian Foster, from PSNI’s Organised Crime Unit, said: “This ongoing NCA-led investigation resulted in a joint operation between police and NCA over the last few days which has uncovered between £10-12m of herbal cannabis.
“This successful operation demonstrates the significant benefits of joint working with law enforcement partners.
“We will continue to work closely with NCA to disrupt the nefarious activities of organised crime groups operating in Northern Ireland.”