The US shop, which was opened seven years ago to service its West Coast-based client Adidas, is being bought out by the agency's president and creative director, Vince Engel, and Wayne Buder, its co-president and managing director.
The New York office is expected to open in the autumn of this year.
Leagas Delaney's chairman, Tim Delaney, will continue to work with the San Francisco office on jointly held clients including Dr Martens and the recently acquired software marketer Nvidia.
Leagas lost the Adidas business two years ago.
Delaney said the move to open in New York had been prompted by client requests increasingly arriving from the US's East Coast. He said: "It's just a quirk of history that we started in San Fransisco.
"Eighty per cent of the US advertising business is based around the East Coast. So this move makes great sense, as we want to focus on New York and the growing opportunities we have with our clients there."
The Italian coffee giant Illy is one of Leagas Delaney's clients that is currently based in New York. Leagas Delaney won the brand's global creative business in April after seeing off competition from the Milan offices of Young & Rubicam and Saatchi & Saatchi.
Meanwhile, Leagas Delaney's Nick Hough, the deputy chairman of Europe, is leaving to pursue a career outside advertising after more than 20 years in the industry.
Pascal Gregoire, the chairman of the Leagas Delaney Paris office, will replace him.