The site owned by Global Energy Group joins Wick Harbour in Caithness in securing work on the Â£2.6bn Beatrice Offshore Windfarm Ltd (Bowl) project.
Siemens, one of the companies involved in Bowl, will use the yard for assembling turbines from spring 2018.
Once assembled the turbines would be towed out to the wind farm site.
The project, which also involves energy giant SSE, is to be created about eight miles off Wick.
Global said Nigg's involvement would help to secure work for more than 100 people.
The Scottish government, Highland Council, Highlands and Islands Enterprise, Scottish Council for Development and Industry (SCDI) and Scottish Renewables have welcomed the announcement.
Business, Innovation and Energy Minister, Paul Wheelhouse, said: "Offshore renewables represent a huge opportunity for Scotland; an opportunity to build up new industries and to deliver on Scotland's ambitious renewable energy and carbon reduction targets for 2020 and beyond.
"I am delighted that this multi-million pound contract between Global Energy Group and Siemens will enable Nigg Energy Park to develop into a genuine multi-energy site, securing around 100 direct and indirect jobs and associated supply chain opportunities.
"This contract arising from installation of the Beatrice Offshore Wind farm will provide a very welcome boost to the local economy in Ross-shire and the wider Highland Council area."
Regional director for the Highlands and Islands, Fraser Grieve, said: "Today's announcement of Nigg's involvement in the Beatrice Offshore wind project shows the positive economic impact that this major development will have on the region over the coming years.
"Nigg, and the wider Cromarty Firth, has much to offer and this agreement is not only a boost for the Global Energy Group but will benefit the supply chain through the area."
Lindsay Roberts, senior policy manager at renewable energy industry group Scottish Renewables, said: "The contract signed today will help breathe new life into this Highland port.
"Scotland's offshore wind industry has huge potential for both our economy and our environment, and it's great to see Nigg reaping the benefits.
"As other wind farms with planning consent in the Scottish North Sea begin to develop, agreements like this will play a key role in securing benefits not just for communities on the east coast, but for the whole of Scotland."
The Nigg Energy Park on the Cromarty Firth is to be used during construction of an 84-turbine offshore wind farm.