Dubois, acquired in a trade with the Winnipeg Jets on June 27, scored on a one-timer from the right circle 8:27 into the first period to give the Kings a 1-0 lead.
Adrian Kempe scored 17 seconds into overtime. Anze Kopitar had a goal and an assist, and Pheonix Copley made 24 saves.
Mike Hoffman scored his first goal for the Sharks, who finished the preseason 2-2-2. Mackenzie Blackwood made 33 saves.
Alexander Barabanov deflected Mikael Granlund’s point shot on a power play to tie it 1-1 at 17:39.
Kopitar gave the Kings a 2-1 lead at 8:16 of the second period after a steal and pass by Drew Doughty.
Hoffman tied it 2-2 for the Sharks at 14:45 with his first goal with San Jose, putting in a rebound. The forward was traded from the Montreal Canadiens as part of the three-team deal that sent Erik Karlsson from the Sharks to the Pittsburgh Penguins.
Trevor Moore gave Los Angeles a 3-2 lead at 3:28 of the third period on a one-timer from the slot.
Thomas Bordeleau tied it 3-3 at 14:15.
