Lucas Fancy scored the game-winner with less than four minutes to play in the second period as Leamington nipped LaSalle 2-1 Thursday night in the Greater Ontario Junior Hockey League.
Jacob Kalandyk scored the other goal for the Flyers, while Spencer Lecot had the Vipers' lone goal.
Matthew Waite made 24 saves to pick up the win, and Sami Molu stopped 30 shots for LaSalle.
Leamington (15-4-0-1) moved to within two points of first-place London in the Western Conference standings, while the Vipers (10-8-1-2) are fourth, 10 points back of the Nationals.
It was the back-half of a home-and-home series between the Essex County rivals, which saw the Vipers win Wednesday night at the Vollmer Centre.