Greens captain Aston Young, son of former island player Craig, scored twice, with Theo Cooper and Jake Martin getting the other Guernsey goals.
Having fallen behind, Guernsey turned it around to lead 2-1 before a late leveller from the hosts took the game into extra time.
But Cayden Tardif’s side then found another gear as Young and then Martin took the game away from Jersey.
It is the first time Guernsey have won the fixture since a 1-0 win on Sarnian soil back in 2017.
More to follow.
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