Donald was fined a total of $42,540 after grabbing a facemask in the fourth quarter of the Rams' 24-3 loss to their NFC West rivals. The Pro Bowl selection was then whistled for unsportsmanlike conduct for picking up the flag and throwing it back at the official.
The league docked the 25-year-old Donald $18,231 for the unnecessary roughness and $24,309 for the manner in which he "returned" the flag.
Donald has been fined $82,040 this season for five separate incidents, including crashing a kneel-down against the Detroit Lions in October and two infractions that led to his ejection in Week 1 versus the San Francisco 49ers.
Donald has a team-leading seven sacks to go along with his 42 tackles this season for the Rams (4-10), who host the 49ers (1-13) on Saturday (4:25 p.m. ET).