Shead initially signed with the Lions in free agency in March, but a strained quadriceps injury sidelined him for two preseason games. Shead was released by the club earlier this month.
The 30-year-old Shead's return is expected to provide depth as star cornerback Darius Slay deals with a concussion. Slay's availability is in question as the Lions (0-2) host the New England Patriots (1-1) on Sunday (8:20 p.m.).
Shead has recorded 154 tackles, four forced fumbles, one sack and 24 passes defensed in 54 career contests with the Seattle Seahawks. He was limited to two tackles in two games in 2017 after missing the majority of the season following an ACL tear in the playoffs of the previous campaign.
Shead originally entered the NFL in 2012 with the Seahawks as an undrafted rookie free agent out of Portland State.
Also on Wednesday, Detroit signed wide receiver Keon Hatcher to the practice squad and released linebacker Alex Barrett from the practice squad.
Hatcher joins the Lions after appearing on the roster for the Oakland Raiders' season-opening game versus the Los Angeles Rams. He originally entered the NFL in 2017 with Oakland as an undrafted rookie free agent out of Arkansas.