Secretary of State William Galvin says by giving the information to certain large U.S. hedge fund and institutional clients in advance, it allowed them to profit from weaker sales of Apple iPhones.
Galvin says Citigroup Global Markets violated its own policies and procedures as well as federal and state securities laws.
The settlement was filed Wednesday.
Galvin had the authority to pursue Citigroup because the company is registered to conduct business in Massachusetts.
Citigroup said in a statement it is "pleased to have this matter resolved." The analyst has been fired.