The new office on Fifth Avenue brings it closer to clients such as the World Gold Council and Aberdeen Asset Management, among others.
Benton-Sullivan, head of Americas, who already runs the office Cicero opened in Washington DC in 2010, will be heading up both offices in the US.
He said: "This move puts us on the porch of some of our largest established clients on Wall St and across corporate North America. We are already offering integrated counsel to some big names and intend to drive forward expansion of our offer."
Iain Anderson, director and chief corporate counsel, said: "Our New York office is the obvious next step in the Cicero story as we continue to expand our multi-sector, international services into exciting new markets."