Real estate investment trust Hibernia REIT has agreed to lease all the office accommodation in 1 Sir John Rogerson's Quay to HubSpot, which develops amd markets software products.
HubSpot is taking a 20 year lease starting in June.
1SJRQ is a high profile riverside development and is due to be completed early next year.
It will comprise 112,000 square feet of offices and 7,000 square feet of food and beverage space.
It is one of six adjacent properties owned by Hibernia which make up the Windmill Quarter in Dublin's South Docks and which will total about 400,000 square feet of office space along with further residential and recreational areas when finished.
The announcement was made as Hibenia REIT reported net rental income of €26.6m for the six months to the end of September, up 21.5% over the same time last year.
The REIT said its portfolio value stood at €1.330 billion at the end of September, up 3.9%.
The company reported a profit before tax of €64m, which it said included a revaluation surplus, while it generated sales proceeds of €55.6m in the six month period.
It has declared an interim dividend declared of 1.5 cent per share, up 36.4% on the previous year's inteirm divident of 1.1 cent.
Kevin Nowlan, the chief executive of Hibernia, said the company's portfolio returns have continued to outperform the market and it has made good progress with its committed developments and its pipeline of future schemes.
"With the letting of 1SJRQ to HubSpot we have de-risked over half our current development programme and our contracted rental income and average lease duration have grown to record levels," he said.
"We continue to recycle capital into assets which we believe will enhance our future returns: in particular we are excited by the potential at Newlands Cross, where we now control 143.7 acres of land," he added.
Mr Nowlan said the company is looking to the future with confidence.
"There is a high level of demand for office and residential space in Dublin, both from tenants and investors, and the Irish economy is growing strongly. Our portfolio is rich in opportunity, we have flexible low-cost funding in place and a talented team," he added.
Shares in the company moved higher in Dublin trade today.