Workers at Sports Direct's Derbyshire base will receive back-pay of about £1m for non-payment of the minimum wage, according to the Unite union.
The distribution centre in Shirebrook has been under scrutiny over its "Victorian" working practices.
Unite said the payments, back-dated to May 2012, could be worth up to £1,000 for some workers.
Sports Direct boss Mike Ashley admitted workers were paid below the minimum wage when he faced MPs in June.
The billionaire owner of Newcastle United made the admission during a hearing before the Business, Innovation and Skills select committee.
Unite assistant general secretary Steve Turner said it was a "significant victory" but warned that it did not mean everything was "rosy" at the warehouse.
The union said about 1,700 Transline agency workers at the Derbyshire site may only initially receive half the back-pay they are owed because of the firm's refusal to honour its commitments from when it took over from Blue Arrow in 2014.
A Transline spokesman said: "We are making all payments required in full compliance with HMRC [HM Revenue and Customs]."
Workers directly employed by Sports Direct and the Best Connection agency are expected to start receiving back-pay in full towards the end of August, Unite officials said.
Sports Direct has been approached for comment.