Kelly signed a four-year, $12 million extension. Campbell agreed to a three-year, $4.8 million deal.
The third- and fourth-line centers have been valuable niche players. Kelly is an alternate captain coming off a career-first 20-goal season. Campbell has teamed with Daniel Paille and Shawn Thornton to form a consistent fourth line. Both have been regular penalty-killers.
The Bruins are not expected to sign any more of their pending UFAs prior to July 1.