Ruhwedel was a restricted free agent after the Sabres retained his rights by making him a qualifying offer last month. The team announced the signing on Wednesday.
Ruhwedel split last season playing for the Sabres and their American Hockey League affiliate in Rochester. Overall, he has one assist in 28 NHL games, and four goals and 24 assists in 47 AHL games.
The Sabres signed the University of Massachusetts Lowell product in April 2013 after Ruhwedel completed his college career.
He's shown signs of being a dependable two-way defenceman and has an opportunity to make the Sabres' lineup this season.