Marrone replaces Chan Gailey who was fired last week.
"It's another dream come true," said Marrone during a noon press conference. "I'm excited to work with the players."
Marrone, who played in the NFL and was an assistant coach in the league for seven years, was the Syracuse coach for the last four seasons. He was 25-25 over that time with two Pinstripe Bowl victories.
Marrone says he plans to hire offensive and defensive coordinators with NFL experience.
In a joint statement, Syracuse Chancellor and President Nancy Cantor and SU Board of Trustees Chairman Richard Thompson said, "We congratulate coach Marrone on having this opportunity to become a head coach at the highest level. Under his leadership, we have restored the rich, winning football tradition at Syracuse, and we wish him continued success as he moves to the National Football League."
They added they are committed to finding Marrone's successor at SU and identifying the candidate to keep the program on its upward trajectory.
Sports Director John Kucko and Thad Brown are in Buffalo for the announcement and will have full coverage of Marrone's introduction as the new Bills coach throughout the day on News 8, beginning with First at Four.