The Dutch-based offshore service company paid approximately £40 million ($51.95 million) for Gardline, including assumed debt, it announced.
Earlier this month, ScottishPower Renewables awarded Gardline contracts to carry out pre-construction surveys across the East Anglia One, One North and Two offshore projects, off the UK's east coast.
Gardline has also been charged with carrying out a geophysical survey in Massachusetts, US, for the Vineyard Wind project, half of which is owned by Avangrid Renewables, ScottishPower Renewables' American-sister company.
The surveyors hire about 750 employees at its sites in USA, Brazil, Singapore, and at its primary base in Great Yarmouth, UK.
The acquisition helps Boskalis to "fulfil its strategic ambition" of becoming a specialist provider of offshore surveys for the renewables market as well as the oil and gas markets, the firm said.
Boskalis does not expect the takeover to turn a profit after interest and tax for a "few years", the company added.
In 2015, Boskalis had upped its stake in Fugro — a Gardline competitor for marine surveys in Europe — to more than 20%, but divested its stock in the Dutch company in March of this year.