About 800 members of Chicago Teachers Union's House of Delegates backed the deal in a voice vote Tuesday afternoon, the Chicago Tribune reported.
Crain's Chicago Business newspaper said two school district sources told it the union delegates had voted to send members back to work before rank-and-file members cast ballots on the tentative contract.
The delegates met behind closed doors to decide whether to end the first teachers strike in the nation's third-largest district in 25 years.
The walkout, which affected 350,000 students and about 26,000 school district teachers and other staff, hit its seventh day of classes Tuesday.
Chicago Mayor Rahm Emanuel went to court this week seeking an injunction to force teachers back into the classroom. A judge held off ruling on the request until Wednesday.
Emanuel contended state law prohibits teachers from striking over non-economic issues -- including layoffs and teacher evaluations.
The New York Times said the dispute centers on local concerns over job security, evaluations, pay and working conditions.
Parents delivered more than 1,000 postcards to the Chicago Board of Education Tuesday calling for an end to the strike. About 50 parents handed the postcards to security guards after schools Chief Executive Officer Jean-Claude Brizard did not to come downstairs to accept them, WBBM-TV, Chicago, reported.
"I'm hoping the delegates come to their senses and know that our kids need us," CPS social worker Mary Silva told the Tribune outside school headquarters.
The union delegates' decision came two days after deciding not to accept a deal struck by negotiators.
School district attorneys filed hundreds of pages of court papers Monday in a lawsuit alleging the union's 26,000 members had no legal basis to declare the strike.
The union called the lawsuit a "vindictive act."
"This attempt to thwart our democratic process is consistent with Mayor Emanuel's bullying behavior toward public school education," a union statement said. "If this was an illegal strike, the Chicago Public Schools would have sought injunctive relief on Day One."