Pepco and its union said they have reached a tentative contract agreement that will likely avert a strike.
The preliminary agreement is subject to a vote by the International Brotherhood of Electrical Workers Local 1900, Pepco said.
"After extended negotiations over the weekend, Pepco and Local 1900, IBEW, have reached a tentative agreement," Pepco spokeswoman Myra Oppel. "The tentative agreement is subject to ratification by the union membership. The ratification vote is expected to take place in the near future."
The union posted a message on its website Sunday saying they had reached an agreement on a four-year contract after daylong negotiations.
Both sides declined to provide specific details on the agreement.
Union President James A. Griffin said the union leadership is recommending that members vote to approve the contract. Previously he said his biggest concern was a proposed change to the workers' health and welfare plans.
The company and union were at an impasse for months. The company's previous offer was rejected 5 to 1 in a vote last month.