Two Sydney men have been fined nearly $8 million for smuggling prohibited tobacco and cigarettes into Australia.

Customs and Border Protection says Dory and Ronnie Karam tried to import a container with a declared cargo of shoes on August 2, 2007.

Customs officers found 150,000 cigarettes and 12,926 kilograms of unprocessed tobacco leaf inside.

In the NSW Supreme Court on Friday, the Karams were convicted of attempted smuggling and other offences and fined $7,954,914, customs said in a statement.

National Manager of Investigations, Kingsley Woodford-Smith, warned of the seriousness of cigarette smuggling and importing illicit tobacco.

"This was an attempt to deprive the government of legitimate revenue," Mr Woodford-Smith said.

"The large penalty incurred should be a warning for others thinking of committing similar crimes."