McNeill, a two-time Pro Bowl selection, missed San Diego's first two regular-season games while hoping for a larger contract and will still be sidelined for the next three contests as he was placed on the team's roster exempt list.
"We're all very happy that Marcus McNeill has decided to sign his tender and go back to work," Chargers general manager A.J. Smith said. "He has missed some time on the job, but we will be patient, get him up to speed and coach (Norv Turner) will decide how quickly he gets on the field."
McNeill was the Chargers' second-round pick in the 2006 draft out of Auburn and has missed just two games during his four-year career, starting all 62 games he has appeared in.
Wide receiver Vincent Jackson has yet to sign.
•The Packers listed left tackle Chad Clifton (knee) and left guard Daryn Colledge (knee) as probable for Monday night's game against the Bears.