Boosted by the return of several players who have missed recent games, Knights found themselves under early pressure.
But they weathered the pressure and went close themselves from a driving lineout late in the first quarter.
Last season’s runners-up broke the deadlock with a 25th minute try by scrum-half Kieran Hardy who darted through a narrow gap.
Brendan Cope added the extras.
The visitors failed to capitalise on a couple of decent moves prior to falling further behind just before the break when Tom Pincus touched down for an unconverted try from a kick to the corner.
But with the wind at their backs in the second half,.
Knights – for whom Simon Humberstone and Curtis Wilson linked well in the opening minutes - remained in the game.
That was even more the case when Dougie Flockhart kicked a long-range penalty on 53 minutes to cut the deficit to 12-3.
Knights lost key jumper Tom Hicks, who was one of several changes, prior to Hardy bagging a second try on 57 minutes from a well-worked move from a lineout.
Despite further injuries Knights continued to battle but they never looked like making inroads into Jersey’s 14-point lead.
They fell further behind with a try from a forward drive ten minutes from time which served to hammer the final nail into their coffin.
The 2015 runners-up did have the final word, however, with hooker Ben Hunter (inset) breaking from the back of the maul to score near enough for Flockhart to convert.