Leino, 27, recorded career bests in points (53), goals (19), assists (34) and powerplay goals (five) in 81 games with Philadelphia last season.
"We felt very strongly about Ville. We felt it was important to make sure we didn't allow a quality player like him to slip by us," Sabres general manager Darcy Regier told reporters.
Terms of the deal were not disclosed.
(Reporting by Gene Cherry in Raleigh, North Carolina. Editing by Tony Jimenez)