A Ross Allen penalty five minutes before half-time was enough to beat Jersey and earn Guernsey their first Muratti Vase success since 2005.
The penalty came when Jersey keeper Jimmy Styles, who was only shown a yellow card when it might easily have been red, brought down Dave Rihoy.
Jersey pressed hard in the second half, but the Guernsey defence held firm and rarely looked in danger.
Jersey lead the series 50-42, Alderney having won the cup once in 1920.
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Highlights of the Muratti 2010 final at Springfield
"I've felt like this twice in a week now," said Guernsey captain Sam Cochrane. "We played very well in the first half, very well.
"We believed we could win it, we knew we could win it. We feel like we're a stronger outfit then they are at the moment."
Guernsey manager Tony Vance told BBC Sport:
"The lads have been magnificent for me.
"To be fair to Jersey, they really had a go in the second half and we were dead on our feet.
"I made a few changes and hopefully that worked. We hung in there.
"We've been threatening to do this for a few years now and I'm just delighted we won. It's been a great season."
Jersey manager Jon Welsh told BBC Sport:
"We're deflated. I felt the second half performance deserved something out of the game. One mistake has cost us the Muratti.
"I think everyone that was here would have seen second half we were the better side.
"First half we didn't play as well as we could have played, but we were a bit unlucky."
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