The Department of Agriculture and Rural Development (DARD) has been given the green light to build its new headquarters in Ballykelly.
Planning permission for the 8.7-acre site was granted yesterday by Causeway Coast and Glens Borough Council Planning Committee.
Work is expected to start this summer, with a view to moving staff into the three-storey building by the end of 2017.
But the Ulster Farmers' Union says it still has reservations over the HQ move, saying it could result in an exodus of highly experienced staff even though there is an existing network of DARD Direct offices across Northern Ireland that could be used.
Agriculture Minister Michelle O'Neill said: "I am delighted we've got approval to start building our new modern headquarters on the former Shackleton army barracks in Ballykelly.
"We will now appoint a building contractor and hope to see construction work begin at the site in the summer with the three-storey building ready for new staff at the end of 2017.
"Today's news is a vital step towards achieving our goal of a £20m investment in relocating public sector jobs to the north west as well as an economic boost to traders, businesses and the wider community.
"I hope the building will become part of village life so I have ensured it is designed with facilities that can be used by the local community."
The move from Dundonald House in east Belfast to Ballykelly will begin next year.
Ms O'Neill said: "Work has already begun on plans to relocate staff as well as identifying staff who want to move to Ballykelly. My department has already permanently relocated a number of people in the north west as part of an advance relocation group.
"The level of interest in this location is extremely encouraging and I have no doubt will make a big difference to people living in the north west."
The building is designed to be framed by bronze cladding sitting on a base of stone walls.