The stadium will become a multi-use venue, and is due to host five matches during the Rugby World Cup next year. It'll also be the permanent home of West Ham United from 2016.
Balfour Beatty already has a £41m roof contract for the stadium, which it was awarded in the summer. Once reconfigured, the cantilevered roof will be the biggest in the world, measuring 84 metres at its deepest point.
The deal will also see the company work with Newham Council's employment service - 400 people will be employed by the project, when construction is at its peak.
Andrew McNaughton, chief executive, said:
During construction, our firm commitment to the use of local labour and the creation of apprenticeships will continue to benefit the local community and the wider industry.