The company is set to move into the new premises in September, having been in Dublin in temporary offices since autumn 2011.
The new office is part of Ancestry's long-term growth strategy and represents a new investment by the company in its International division which covers the organisation's operations outside of the USA.
Employee numbers in the Dublin office currently total 15 but are expected to grow to more than 50 within two years.
That number will include staff working within management and finance functions as well as website developers and member service agents.
Olivier van Calster, Ancestry.com's VP & General Manager, International comments: "We are delighted to be opening our new offices at Sir John Rogerson's Quay and are looking forward to growing our international business from Dublin. Ireland is the perfect location for our International headquarters and was chosen for a number of reasons, not least because of the great availability of talented people, but also because it is a country that has a long history of emigration and plays a significant role in the family history of people across the globe."