The vote was 36-5, with two abstentions, two union board members said.
"They go back right away," said Transport Workers Union President Roger Toussaint, who was greeted with chants of "T-W-U" as he approached the podium outside union headquarters. He added only that more information would come "in the next several days."
Mayor Michael Bloomberg said he expected workers to return to work for their next shifts -- at 4 p.m. Thursday -- but that it could take between 10 and 18 hours to get the system up to full capacity.
"It can't be turned on or off with the flip of a switch," he said.
The transit workers went on strike early Tuesday, shutting down the nation's largest public transportation system and creating hardships for more than 7 million commuters. The transit strike is the first in the city since 1980.