Enterprise Causeway has invested £700,000 in 12,000 sq ft of Grade A office and networking space as well as a new headquarters.
The firm, which is marking its 35th year, has moved to Kilsandel House in Coleraine.
It said that over the last year, it has helped 123 new start-up companies with the creation of 75 jobs, making an economic contribution of £7.4m in the Causeway area.
The enterprise agency, which recently rebranded, now has a presence over six sites, including Coleraine, Kilrea, Ballymoney, Ballycastle and Bushmills.
Chief executive Jayne Taggart said it was a "significant milestone" for the company.
"The launch of Kilsandel House, a new business, events and networking hub, provides Class A office accommodation for the professional sector in addition to being home to our headquarters and expanding team," she added.
"As well as bespoke office space there are desks available on hourly, daily and weekly rates which can appeal to any number of business people and entrepreneurs.
"With cutting-edge technology available, it can also be used as a fantastic training facility with meeting rooms available for hire. This hub supports the entrepreneur."