With the score knotted at 2-2, Hornqvist gathered in the rebound of a Dan Hamhuis shot, made a move on Kings goalie Jamie Quick and put it past him for the game winner.
Pekka Rinne stopped 18 shots for Nashville, which downed the Kings for the seventh straight time, including five in a row at the Staples Center.
Anze Kopitar and Dustin Brown got the goals for the Kings, while Quick was 28-of-31 in nets in the loss.
The Kings hold the fifth seed in the West.
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