Jersey leapfrogged opponents Nottingham into fifth spot in the Championship with victory at Lady Bay.
The islanders, who still have play-off hopes, were 15-0 ahead at half-time thanks to tries from winger Tom Howe and skipper Pierce Phillips.
Paul Grant and Rob Langley crossed for the hosts to pull them level.
Jersey secured victory, however, as referee Andrew Small awarded them a penalty try when Nottingham infringed at the maul.
Brendan Cope's early penalty had put the island side in front and, when Lawrence Rayner's penalty bounced back off the post at the other end, the islanders broke away with Howe crossing for the score.
Phillips then forced his way over from a maul five minutes before the break to put Jersey in a dominant position.
|Analysis: Tim Pryor, BBC Radio Jersey|
|This result gives Jersey real hope that they can make the play-offs, which would be a remarkable achievement for a club of their size. Three of their last four league matches are at home. Yorkshire Carnegie (fourth) and Bedford Blues (third) will be looking over their shoulders nervously and they still have to face each other later this month.|
The Green and Whites hit back though early in the second period with back-rower Grant crashing over from a maul.
Dan Mugford's penalty reduced the deficit further and then an interception of Nick Campbell's pass saw the hosts run the length of the field and Langley cross for a try, but Mugford's conversion hit the post.
The defining moment was still to come when, as Jersey drove towards the line, the referee showed no hesitation in awarding the penalty-try which turned out to be the difference between the sides.
The result puts Jersey seven points outside the play-offs, with all the teams above them still having a game in hand. Nottingham take a losing bonus point from the match, and are a point behind the Channel Islanders in the table.
Nottingham: Robinson; Skelcey, Woods, Hakalo, Coghlan Murray; Rayner, McConnell; Davies, Vickers, Daniels, Eames, Freeman, Cooper, Langley, Grant (capt).
Replacements: Harris, Carey, Green, Everard, Veenendaal, Mugford, Stevens.
Jersey: Adair; Howe, Evans, Robling, Lane; Cope, Dudley; Lockwood, Buckle, Kerrod, Phillips (capt), Campbell, Haining, Freeman, Kolo'ofa'i.
Replacements: McCarthy, Selway, Herriott, Markham, Spinks, Moates, Penberthy, Owen.