With Commissioner Roger Goodell at the table, the sides concluded two days of talks at midnight Thursday with the announcement of a tentative deal, which must be ratified by the union's 121 members.
NFL spokesman Greg Aiello tweeted "Pleased to report that an agreement has been reached with the NFL Referees Association. Details to follow."
The replacements worked the first three weeks of games, triggering a wave of frustration that threatened to disrupt the rest of the season. After a missed call cost the Green Bay Packers a win on a chaotic final play at Seattle on Monday night, the two sides really got serious.
It was not certain who would work this week's games, which begin Thursday night with Baltimore hosting Cleveland.