The 11-turbine Aberdeen Bay project has been much delayed due opposition to the project from US businessman Donald Trump, who owns a nearby golf course.
Boskalis has been appointed preferred balance-of-plant contractor to oversee construction and installation of foundations and cabling.
And UK engineering firm J Murphy & Sons has been named preferred bidder to provide onshore infrastructure.
The contracts are conditional on a positive final investment decision, which Vattenfall and project partner Aberdeen Renewable Energy Group expect to make by the end of 2016.
The project will use suction bucket foundations, EOWDC project director Adam Ezzamel said.
Trump's third challenge to stop the EOWDC was defeated in December 2015. A panel of UK supreme court judges backed the Scottish government, which gave the go-ahead to the in 2013.
The EOWDC is planned for a site off Aberdeen, north-east Scotland and would be visible from the controversial property tycoon's luxury Scottish golf resort.