Scottish Provident Building in Belfast city centre has reached 97% occupancy after signing two new tenants.
Donna Linehan, its head of sales and customer services, said 60 firms from all sectors are now housed inside the building, which finished a nine-year refurbishment in 2018. "We are always very excited to see new clients but I get a real buzz out of seeing tenants grow within the building," she said.
The company behind the historic Grade A building near City Hall said it "strives to be a catalyst for growth amid an apparent resurgence of demand for traditional office space".
Its latest tenants include foreign and direct investment firm High Roads and Push Technology.
Current tenants Gavin & Doherty Geosolutions and Repstor have taken more space as both businesses expand.
Ms Linehan said she believes the central location is a major pull for tenants, but said the "stunning" architecture of the seven storey building adds to its appeal.
Repstor chief executive Alan McMillen said staff at the company appreciate their "exceptional" workplace there, and continued: "We have had another phenomenal year and our recruitment initiatives have drawn some enviable talent, so it's time to expand to a bigger space."
He added: "This was a very easy decision to stay and grow in this iconic building."
Ms Linehan added that business leaders "could be sure of a great location with great communications, security and service".