Sekera, 25, is coming off his best NHL season, when he scored 29 points and was a plus-11 in 76 games. However, the defenseman was limited to just two games in the postseason against the Philadelphia Flyers, however, due to an upper-body injury he sustained late in the regular season.
The signing avoids an arbitration hearing that had been scheduled for July 25.
A 2004 third-round draft pick of the Sabres, Sekera has 67 points in 233 NHL games since debuting with the team during the 2006-07 season.
Ellis, 29, was scoreless with a minus-4 rating in 14 games last season. The 6-foot, 212-pound left wing had 10 goals and 31 points in 52 games with the Portland Pirates of the American Hockey League.
In 201 NHL games with the Red Wings, Kings and Sabres, Ellis has 13 goals and 33 points.