Mr. Sigel, 42, was previously in charge of the Publicis Groupe agency's stable of financial-services accounts, which include its largest account, Citibank, as well as the New York Stock Exchange and Travelers Insurance. His Fallon resume also includes work on brands including BMW, Qualcomm, EDS and Nuveen Investments.
The 16-year Fallon veteran replaces Mike Buchner, who earlier this year was promoted to chief operating officer.
"David's contributions are enormous and he has proven to be a true leader for our agency," said Pat Fallon, the agency's chairman. "I have every confidence in his abilities for this important role at the agency."