Set to turn 35 in June, the defensive tackle has been the unquestioned heart and soul of the team, as the Bills successfully ended the franchise's 17-year playoff drought.
The longest-tenured player on Buffalo's roster will continue to hold that title for one more season.
The signing will help the Bills along the defensive front which suffered greatly after they traded Marcell Dareus to the Jacksonville Jaguars last season.
The five-year defender, a first-round draft choice of the Carolina Panthers in 2013, agreed to a five-year contract with the Bills.More news: Journalist Sparks Outrage In Egypt After Asking Salah To Shave "Terrorist" Beard
Lotulelei was drafted 14th overall in 2013 by the Panthers and has ties to Bills coach Sean McDermott and general manager Brandon Beane from Carolina.
In five seasons with the Panthers, Lotulelei established himself as a consistent force at the nose tackle position.
The Bills also tendered exclusive-rights contracts to tight end Nick O'Leary, defensive end Eddie Yarbrough, tight end Logan Thomas and cornerback Lafayette Pitts, a source told ESPN.
Lotulelei, 28, has started 75 of 76 games in his career, with 141 tackles (83 solo), 11.5 sacks, five passes defensed, two forced fumbles and two fumble recoveries. Lotulelei is considered a good run stopper but has been overshadowed by Kawann Short in terms of playmaking ability.