The Titans signed Hallett to the active roster Tuesday, Jim Wyatt of the team's official site reports.
Hallett was signed off the Lions' practice squad and played in three games for the team. The safety's most recent appearance in Week 15 netted a career-high 10 tackles (five solo) and one pass defensed. The 25-year-old slots into the Titans' defense as the backup free safety to Kendell Brooks, so he will likely not get as many opportunities as he did as a practice squad elevation for the Lions.