Longwell, who holds the Packers' franchise records for career scoring (1,054 points) and field goals made (226), retired from the league after a 16-year career that also included six seasons with the Minnesota Vikings.
The 38-year-old, free-agent kicker had signed a ceremonial one-day contract with Green Bay Monday so he could officially retire as a Packer.
The University of California product played for the club from 1997-2005, racking up an 81.6 field goal percentage and 376 extra points, also franchise records, while compiling eight straight seasons of 100 or more points.
In addition to kicking for Minnesota from 2006-2011, Longwell also briefly played for Seattle last season.
He retires as the NFL's 13th-leading all-time scorer with 1,687 points.