When Bolands Mills is finished, over 1,000 engineers will occupy the offices, turning it into a centre for engineering.
In 2018, Google purchased the mills.
Both the complex and the neighbourhood have important historical value.
The structures were occupied by revolutionary fighters during the Easter Rising of 1916.
The 3rd Battalion of Irish Volunteers was led by Éamon de Valera and had its headquarters in the neighbouring Boland's Bakery, which is now the Treasury Building.
"The Flour Mills building is steeped in history, and our real estate teams have worked hard to ensure we respect its past, while equipping it for the future," said Adaire Fox-Martin, Head of Google Ireland.
"When Bolands Mills opens fully next year, a mix of shops, eateries, public squares, and community and cultural spaces will bring new energy to this historic site," Ms Fox-Martin said.
The development's debut coincides with Google's 20th anniversary of operations in Ireland.
Here are located the company's European Headquarters, which employs over 9,000 employees in total, 5,000 of whom work directly for Google.
Google eliminated 240 positions in February as part of a global restructuring.
The corporation announced more staff reductions earlier this month.
Some of Google's employees are represented by the Financial Services Union (FSU), which has accused the firm of attempting to enact mandatory layoffs.
Leo Varadkar, the Taoiseach, was present at today's Bolands Mills development's official opening.
"The opening of this historic building is good for Dublin's civic heritage and represents a major milestone for Google Ireland driven from their innovative new centre of engineering," Mr Varadkar said.
The establishment of a €1.5 million scholarship fund for students from underrepresented populations to study artificial intelligence (AI) was also announced by Google today.