According to ESPN's Adam Schefter, the two-year deal is worth $12 million with $11 million guaranteed. NFL Network's Ian Rapoport confirmed.
Timmons recently completed his 10th NFL season with the Steelers, who selected him with the No. 15 overall pick in the 2007 NFL draft.
The decision to take Timmons paid big dividends, as the former Florida State standout has developed into one of the league's best and most consistent inside linebackers.
He made his first Pro Bowl in 2014 after registering a career-high 139 tackles along with two sacks, and he followed that up with another terrific campaign in 2015 that saw him put up 119 tackles, five sacks and one interception.
The South Carolina native continued to establish himself as an elite-level performer in 2016 with 114 tackles, 2.5 sacks and two interceptions.
Timmons seemed destined to serve primarily as an outside pass-rusher when he first entered the NFL. While he has excelled at getting to the quarterback with 35.5 career sacks, he has developed into a fantastic all-around linebacker with six seasons of 100 or more tackles and 12 career interceptions.
He has also missed just two games in his NFL career, which made him one of the few consistently reliable defensive players on the Steelers roster over the past several years.
Despite his impressive resume, major question marks surrounded Timmons' future with the franchise ahead of training camp in 2016.
Per Mark Kaboly of the Pittsburgh Tribune-Review, Timmons and the Steelers were far apart on a new deal, and there was some concern they would allow him to hit free agency and move forward with Ryan Shazier and Vince Williams as the starting inside linebackers.
It now appears the Steelers will move in that direction.
While Pittsburgh's success is predicated largely on the offense led by quarterback Ben Roethlisberger, running back Le'Veon Bell and wide receiver Antonio Brown, losing Timmons potentially weakens a defensive unit that was already suspect to some degree.
Timmons has shown over the years that he can truly do it all, from rushing the quarterback to stopping the run and defending the pass. His remarkable versatility figures to make him a quality signing for the Dolphins.
While Timmons is 30 years of age, the 2016 campaign was one of his best, and every indication is that he has plenty of productive seasons left in him for his new team.
The weak link of Miami's defense has long been its linebacker corps, but that may no longer be the case, as Timmons joins Kiko Alonso (a restricted free agent who Miami seems likely to re-sign) and Koa Misi to form a solid unit.
Transitioning from a 3-4 to a 4-3 could be a challenge for Timmons, and it isn't certain where he will line up, but he figures to have less of a pass-rushing burden with the Dolphins.
Provided the likes of Cameron Wake and Ndamukong Suh dominate up front, it should open up plenty of room for Timmons to make plays.
