Ennis signed a two-year contract worth $5.625 million, according to a person familiar with the contract. The person spoke on the condition of anonymity because the financial terms were not disclosed by the Sabres.
Ennis had been a restricted free agent whose rights had been retained by the team in June.
The deal was reached on a day in which the NHL is prepared to lock out its players if a new collective bargaining agreement is not reached by midnight, when the current deal expires.
General manager Darcy Regier said the threat of a labor disruption played a key role in getting Ennis signed because the team would've been barred from negotiating with the player in the event of a lockout.
"I think with the uncertainty, what it does is it removed one additional piece," Regier said. "Whenever it is we start, Tyler's signed and ready to go, and it's not something that you're going to be pressed into action and negotiating while you're trying to prepare for a season."
The second of Buffalo's two 2009 draft picks, Ennis has been a speedy and gifted playmaker when healthy during his two full seasons with the Sabres. Listed at 5-foot-9 and 172 pounds, he's also overcome initial questions about his lack of size.
Ennis had 15 goals and 19 assists in 48 games last season, but was out of the lineup for two 17-game stretches because of an ankle injury. Upon his return in February, Ennis provided an immediate spark to a sluggish offense by centering a line with Drew Stafford and rookie Marcus Foligno.
Ennis enjoyed a 24-game stretch in which he had 10 goals and 16 assists. Overall, he has 38 goals and 54 assists in 140 career games.
"Talent-wise, he's an upper-echelon player," Regier said. "Obviously, he's got to overcome some issues like size, but he's fearless, he's got a big heart. It's a bit of an unknown, but we certainly have insight that allows us to project him to be a very good player in the National Hockey League hopefully for a long time."
The two sides settled on a two-year deal because they couldn't agree on a long-term contract. Ennis had been seeking a four- or five-year deal that would've averaged about $4 million a season.
"At the end of the day, we looked a multiple different options for him, and we thought the two-year contract was the best fit," Ennis' agent, Eustace King said. "It allows Tyler to prove himself more, but it provides fair compensation."
"I might make the case that in a lot of times these act in the best interest of the player and the club," he said. "It offers additional incentive and certainly he's going to have the opportunity to fulfill that incentive."
Though Ennis split time at wing and center, Regier said the Sabres expect him to start the season at center, even after the team spent much of the past year attempting to improve the depth at the position.
Buffalo acquired Cody Hodgson in a trade with Vancouver in February, and in July exchanged centers, landing Steve Ott in trade that sent Derek Roy to Dallas. The Sabres also used two first-round draft picks to select centers Mikhail Grigorenko (12th overall) and Zemgus Girgensons (14th) in June. Both will be given an opportunity to make the team this season.
The Sabres are already preparing for the potential of a lockout after the team loaned 20 players to Rochester, their American Hockey League affiliate on Friday.
The players loaned to the minors include Hodgson, Foligno and Girgensons, and defenseman Brayden McNabb. Grigorenko is still eligible to play junior hockey, and was loaned to Quebec of the Quebec Major Junior Hockey League.
The Sabres also signed goalie Andrey Makarov to a three-year entry-level contract Friday. Makarov was an undrafted free agent, who went 29-21-1-1 with Saskatoon of the Western Hockey League last season.