Terms of the deals were not disclosed.
There had been questions surrounding the status of both Ruff and Regier after Rochester billionaire Tom Golisano purchased the financially troubled franchise last month, reportedly for more than $80 million.
Sabres managing partner Larry Quinn made it known that a lot is expected of Ruff and Regier.
"We've given them some strong goals," Quinn said. "We have to make the playoffs this year and we told them we want to win a Stanley Cup in three to four years. We don't want to survive here. We want to win and be prosperous and we think this is the team that can do that."
Ruff's contract with the Sabres was set to expire at the end of next month. Regier still had four years left on his contract.
"We need to come to a balance," Golisano said. "We want to win. We have an obligation to the fans to do the best we can, we have an obligation to the players and staff and we have to blend everything together to make something that is viable.
"The moves to keep Darcy and Lindy take us in that direction. I think these guys have the talent and capability."
In six seasons with the Sabres, Ruff has posted a 216-205-71 record. He coached the Sabres to the playoffs in each of his first four seasons, including a berth in the Stanley Cup Finals in 1999.
"It's an exciting day for me again," Ruff said. "It feels like six years ago. I think anytime you go somewhere to coach or come back to coach, you come back for one reason, that's to win. Looking back at last year, I didn't want to leave on that note."
With a finanically strapped payroll to work with, the Sabres have missed the playoffs in each of the last two seasons. They went 27-37-10-8, finishing in last place in the Northeast Division, this past season.
"Last year's season was unacceptable," Ruff said. "It was personally, for myself, embarrassing. We're here to win and we're here to nake the playoffs."
Sabres defenseman Rhett Warrener also is happy to see Ruff returning.
"I'm extremley happy to hear he's coming back," Warrener said. "The other positives that I take out of today are the things that Mr. Golisano and Larry Quinn and Darcy and Lindy have all said. It sounds like we're going to be a team they want to have winning and moving forward. I hope everyone on the team got to see this."
The club's general manager for the last six seasons, Regier had come under fire from fans.
In 2001, Regier traded former captain Michael Peca to the New York Islanders. That deal followed a contract dispute that saw Peca sit out the entire 2000 campaign.
Just a week after dealing Peca, Regier gave into goaltender Dominik Hasek's trade demands and traded the six-time Vezina Trophy winner to the Detroit Red Wings. Detroit went on to win the Stanley Cup in Hasek's only season before he retired.
Before Golisano purchased the Sabres, the club had been run by the NHL since June, after John Rigas and his two sons were indicted on fraud charges following the collapse of Adelphia Communications, the team's major creditor.