Coming off his best game of the season, in which he totaled eight catches for 123 yards and two touchdowns, Thielen is now one of two Vikings players (with guard Dru Samia) on the list.
It is unclear whether the receiver tested positive for the coronavirus or was in close contact with someone who did.
Vikings wide receivers coach Andrew Janocko did not coach in Sunday's loss against Dallas. The team included a line in its final injury report Friday that Janocko would not be in attendance.
The receiver's status for a Week 12 matchup with the Carolina Panthers remains unclear. Last week the Vikings placed fullback C.J. Ham on the reserve/COVID-19 list on Thursday but he was able to play three days later, indicating he was on the list as a close contact, not for testing positive.