Jersey's two-and-a-half year unbeaten home record is over after the islanders lost 26-15 against Ealing Trailfinders.
Winger Owen Bruynseels scored two first-half tries for the visitors either side of a Steve O'Brien touchdown for Jersey.
Prolific Ealing try-scorer Phil Chesters scored between the posts soon after the break to increase the lead.
Long periods of pressure and tries from Ashley Maggs and Brendan O'Brien were not enough to extend Jersey's home run.
The last time they had tasted defeat at St Peter was in March 2009 against Tring.
The island side slip to ninth in the National League One table whilst unbeaten Ealing are up to second spot.
Jersey's head coach Ben Harvey said: "With the amount of mistakes that we were making I never felt we were really totally controlling the game for long enough periods.
"It was just a huge amount of errors that we made that added up and you can't get any continuity in your play."