The move opens $3.9 million in 2016 salary-cap space for the Bills, who have been aggressively creating space this week after entering the month with the NFL's tightest salary-cap situation.
McKelvin's release comes after the Bills released three veterans Tuesday -- defensive end Mario Williams, guard Kraig Urbik and running back Boobie Dixon. The team also restructured the contracts of tight end Charles Clay and safety Corey Graham.
The Bills took a big step in addressing their own needs Friday as starting left tackle Cordy Glenn signed his franchise-tag tender for one-year at $13.7 million.
McKelvin, 30, saw action in nine games last season after being activated from the non-football injury list in November -- the result of a broken ankle that ended his 2014 season almost a year earlier. He started five games last season, one at safety and the final four contests at cornerback in place of the injured Stephon Gilmore.
The 2008 first-round pick played in 98 games over the past eight seasons for Buffalo, making 60 starts. His role with the Bills, however, was less certain heading into next season, the final year of his contract extension signed in 2013, following the emergence of 2015 second-round draft pick Ronald Darby.