Authorities say they seized 725 grams of fentanyl from a home in Mastic Beach that had been shipped there from China.
Three men have been arrested in connection with the investigation.
Fentanyl is up to 100 times more powerful than heroin.
"That's over 1.1 million doses of fentanyl that aren't being used in our communities and that saves thousands and thousands, potentially hundreds of thousands of lives," said Commissioner Timothy Sini, Suffolk County Police.
Police say they first discovered the drug operation after intercepting two packages of narcotics at JFK Airport destined for the home in Mastic Beach.