Guernsey beat 10-man Jersey 2-1 to win the Under-21 Muratti at Footes Lane.
Jack Griffin gave Guernsey a 38th-minute lead as he tapped in at the near post after a corner before Jersey's Barry Beatson was sent off for a second booking three minutes later.
Despite being a man down Rai dos Santos equalised soon after half time.
But Keene Domaille's cool finish with 15 minutes to go ensured Guernsey won the Ambassadeur Bowl for the first time since 2019.
Jersey missed a number of chances with Luke Coutanche having an early effort cleared off the line and Dos Santos going close after half an hour.
Patrick O'Toole fired over with 10 minutes left after being put through on goal while Seaney McColgan had an effort cleared off the line in the final moments.
The result means Guernsey take their tally to 19 Under-21 Muratti titles, while Jersey have won it 15 times.
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