The union didn't release details of the agreement, which is subject to a vote by union members.
"We are pleased to have reached this tentative agreement that achieves the required $195 million in annual cost savings from our flight attendants," said Northwest President and CEO Doug Steenland.
Northwest said it expected the union to finish voting on July 31.
"With the airline in bankruptcy, this deal was always going to be about survival," said Mollie Reiley, interim president of the Northwest branch of the union. "We left no stone unturned and we have made a significant difference together, but this is not a day that we celebrate. We have an agreement that will give flight attendants hope for the future and one that allows us to fight another day."
Danny Campbell, interim vice president of the Northwest branch of the Association of Flight Attendants, said a quick vote was in the flight attendants' best interests.
"We need to move on with trying to get the company out of bankruptcy so we can put up a good battle in the future for getting back some of the things we gave up," he said.
A bankruptcy judge had given Northwest permission to impose a contract on Monday that 80 percent of flight attendants had rejected last month. The union had threatened to strike if that happened, putting the airline in even more financial danger.
"It was down to the wire, and we made some improvements, and we just hope they're good enough" for union members to approve, said Sean Fivecoat, the secretary-treasurer for the Northwest branch of the AFA.
Northwest filed for bankruptcy protection in September, and negotiated in earnest with its large unions as it tried to save $1.4 billion a year in labor expenses.
That target included $195 million in savings from flight attendants through wage cuts and work rule changes. Flight attendants were the last union at Northwest without a new contract.
Northwest got the dollar savings it was looking for from all its other unions, and labor experts had predicted Northwest would not back down on its demand from flight attendants, either.
The agreement was made with a union that has only been on the property since July 6, when flight attendants dropped their old union and switched to the AFA.
Northwest has new contracts in place with all its other unions, although the pacts with pilots and ramp workers and ticket agents are on hold until the new flight attendant contract takes effect.