Weston Hodkiewicz of the Green Bay Press-Gazette reports that the Packers signed Mulligan, a four-year veteran, to a one-year deal.
Mulligan has appeared in 50 career games. Not tendered as a restricted free agent in 2012 with the Jets, Mulligan signed a two-year deal with the Rams. St. Louis cut him last month.
In the two seasons, Mulligan has appeared in all 32 games, starting 18.
The Maine product has worked as both a run-blocker and a pass-catcher. He also provides depth at the overlooked-until-the-starter-gets-hurt position of long snapper.
Mulligan reportedly picked the Packers over the 49ers, who are trying to replace the versatile Delanie Walker.