Jersey ran in 11 tries to thrash Guernsey 73-5 in the Siam Cup.
James Copsey and Donovan Sanders both scored hat-tricks for the hosts while Ed Dawson went over twice.
Ross Kenwright, Dave McCormack and Michael Le Bourgeois grabbed one each and Le Bourgeois also converted nine of the 11 scores.
Guernsey got a last-minute consolation when Jason Morgan went over in the corner - the Sarnians first points against Jersey since 2009.
"I'm delighted because it means so much to everyone in the island. To put 73 points on Guernsey is a fantastic achievement," said Jersey coach Ben Harvey, whose side finished second in National League Two South.
Harvey's side will now focus on the league play-off final on 28 May where they will host either Loughborough Students or Leicester Lions.
Guernsey, who won London Two South West last month, could not cope with the power and precision of their higher-ranked opponents.
"I think they're proud of the season they've had," said Guernsey team manager Mike Marshall.
"They worked hard today, but they were against a far superior side and the difference in leagues showed the difference in the teams," he added.
Jersey were rocked by a hamstring injury to experienced flanker Steve O'Brien during the first half. Jersey rout Guernsey in Siam Cup
The Irishman, who was making his 12th Siam Cup appearance, is unlikely to be fit in time for the National Two play-off clash.
"Should Steve be out it'll be a big loss to us," Harvey said.
"He's had a terrific season and he's been playing tremendously well. Luckily we've got young Charlie Clyde-Smith and Graham Bell who can fill that spot very well," he added.