Transocean, which owned the Deepwater Horizon oil rig, pleaded guilty to violations related to the 2010 oil spill, one of the largest incidents of its kind in world history.
Eleven workers died and thousands of barrels of oil spilled into the gulf waters for several months after an explosion sank the rig in April 2010.
"The Deepwater Horizon explosion was a senseless tragedy that could have been avoided," Assistant Attorney General Lanny Breuer said in a statement.
Transocean admitted in the U.S. District Court for the Eastern District of Louisiana to failing to investigate whether the failed Macondo well beneath the rig was secured properly.
Transocean in January agreed to pay a $400 million criminal fine and $1 billion in civil penalties. BP in November agreed to plead guilty to 14 criminal charges stemming from the accident as well as to $4 billion in fines and penalties.
The Justice Department said most of Transocean's settlement was designated for gulf restoration projects as outlined in a 2012 sustainability measure dubbed the Restore Act.
Contractor Halliburton last year was accused of destroying test results regarding cement used to seal the Macondo well beneath the rig. Halliburton said the charges are baseless.
There was no statement on the guilty plea from Transocean, which has headquarters in Switzerland.