It will carry out infrastructure works, including building access roads, cable works and turbine foundations, for ScottishPower Renewables.
The work will be carried out at Harestanes windfarm in Dumfries and Galloway and Middleton wind farm in East Renfrewshire.
Northstone is also the main contractor on a £50m contract for a new terminal for building off-shore wind turbines at Belfast Harbour, a 50-acre facility.
Northstone employs around 900 people and is a subsidiary of Cement Roadstone Holdings (CRH), Ireland's biggest trading company.
The subsidiary enjoyed a turnover of £285m in its latest accounts.