The group said the sale is "in addition to the disposals programme" announced in February where stakes in some of Ballast's other subsidiaries were put up for sale.
The sale of Ballast Nedam Offshore includes all engineering and construction staff. The group's inspection and maintenance operations will be unaffected by the sale.
In the first half of 2014, Ballast Nedam reported a EUR 51 million net loss. A refinancing strategy included EUR 110 million in loans. At the time of the H1 financial report in July, Ballast said the sale of some subsidiaries will be used in part to pay back loans.
Ballast Nedam said its offshore unit had "yielded positive results" since 2006. The unit had worked on the Butendiek, Anholt and London Array projects.
This is the second major offshore vessel sale this month. German construction firm Hochtief sold its entire fleet of offshore wind vessels to GeoSea.