Cargo vessel MV Rena struck a reef off New Zealand in October 2011, spilling about 2,000 barrels of oil into the Bay of Plenty. It has since broken apart and salvage teams are working on what remains of the vessel.
Maritime New Zealand, the agency responding to the disaster, had removed most of the oil from Rena by December.
Daina Shipping Co., the ship's owner, entered a guilty plea to charges related to the discharge of harmful substances. The company was fined $300,000.
"The completion of this prosecution marks another step in the response to the grounding of the Rena," MNZ Director Keith Manch said in a statement. "There remains a lot of work to be done in the recovery process and MNZ continues to oversee the wreck removal process."
Wellington early this month reached a $22.8 million settlement with Daina Shipping Co. regarding last year's incident.
Two of Rena's crewmembers were given prison terms in May after pleading guilty to 11 charges related to the grounding.