There are few details available about the New York office, but it will open with at least two clients, in footwear brand Doc Martens and Nvidia, which makes graphics software.
The accounts are both recent wins and were previously handled in the US by Leagas Delaney's San Francisco office.
Tim Delaney, agency founder and chairman, said: "This makes great sense as we want to refocus on New York and the growing opportunities we have with our clients on the East Coast."
As yet no staff have yet been recruited to run Leagas Delaney's New York office and it is unclear as to whether any senior staff from Leagas Delaney London will head to the States.
Last month, creative hotshop Mother said it was planning to open a New York office.
The San Francisco office of Leagas Delaney is to be bought out by its management, and headed by Vince Engel, president and creative director, and Wayne Buder, co-president and managing director. The agency will be renamed and will continue to work on clients including Monterey Bay Aquarium.
According to Engel: "This was an opportunity we couldn't pass up. How often do you get the chance to build on the creative legacy of the Leagas Delaney brand while putting your own imprint on a business and on an incredible client roster."
Leagas Delaney set up its San Francisco office in June 1996 following the agency's win of the global Adidas account, which it went on to lose to TBWA in 2001.
In 2001 as Leagas negotiated its sale to Canadian company Envoy Communications, which later collapsed, it lost four senior executives at the San Francisco office, who quit over disagreements about the deal.
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