The announcement came as Africa's number one oil producer tries to get tough with illegal oil dealers, as part of a wider crackdown on endemic corruption
The seven -- all of them Nigerian nationals -- were among the crew of the MT Good Success, which was stopped by a navy patrol boat off the coast of Lagos in February last year, the EFCC said in a statement.
On board was some 1,495 tonnes of Premium Motor Spirit (petrol/gasoline).
Judge OE Abang sentenced them to 10 years in prison on each of the first four counts and two years on the fifth, to run concurrently.
He described them as "lawless" and said he hoped the sentence would serve as a deterrent.
The petrol on board, nearly USD 1.7 million (1.5 million euros) held by one of the defendants and the vessel itself were ordered to be forfeited to the Nigerian government.
President Muhammadu Buhari has described the extent of oil theft in Nigeria as "mind-boggling" and estimated some 250,000 barrels of crude were stolen every day under the previous administration.
But analysts agree there are no exact figures for the extent of the problem.
A 2009 report called "Blood Oil in the Niger Delta" said oil is often "tapped" from pipelines or the wellhead in the oil-producing south, then transferred onto barges and taken out to sea, where it is loaded onto large ships.
Companies sometimes pump more oil than their licences allow, before it is processed at illegal refineries in a process implicating company workers and government officials.