A short-corner routine led to a cross from Matteo Ruggeri, allowing Sørloth to slot the ball past the goalkeeper for his third goal.
With a two-goal cushion, Atletico are set to face either Liverpool or Tottenham Hotspur in the last 16.
Atletico Secure Last 16 Spot as Sørloth Bags Hat-Trick
Alexander Sørloth scored a hat-trick to put Atletico Madrid in a commanding position for the Champions League last-16 draw.