Bill Belichick started as head coach of the New England Patriots in 2000, making him the longest-tenured active coach in the NFL.'
The second closest is Mike Tomlin, who was hired by the Steelers in 2007.'
Belichick had an earlier stint with the Patriots prior to being hired. After being fired by the Browns, Bill Belichick took a job as assistant head coach under Bill Parcells in 1996.'
Bill Belichick's record as a head coach is 329-165.