The Reds made it three Championship wins in succession, edging a tense encounter in difficult conditions at the Mennaye by the narrowest of margins.
It was former Cornish Pirate Aaron Penberthy who sealed the result, slotting a penalty with 10 minutes to go - with his first touch of the ball after coming on - which regained the lead for his side, and which they held during the tense closing stages.
The match was very reminiscent of the contest two seasons ago, also in March, when the Reds won 5-7. Callum Sheedy's conversion of a Sean McCarthy try made the difference that day; this time the Pirates had four shots at goal, but Will Cargill could only land one conversion, and his three missed penalties were crucial.
Playing in their blue away kit, the visitors scored first after 20 minutes when a penalty was fired close to the Pirates 22 by Brett Herron. The Jersey maul was slow to start with, but then Charlie Maddison splintered off the front, found Jerry Sexton in support and the skipper fed Will Homer for a short dash to the corner.
The home side responded strongly and when Tom Duncan set off from the back of a scrum, the number 8 also had the pace to follow up and score after a fast break down the left-hand touchline by Matt Evans.
The Reds were solid in defence throughout the afternoon, while the Pirates had to contend with a misfiring lineout that has proved an Achilles heel this season. Having played into a diagonal wind for the first 40 minutes, the visitors were pleased to snuff out a final attack and head to the dressing rooms.
Pirates defied the conditions during a strong opening to the second half, which twice yielded penalty chances near the Jersey 22. But both times Cargill pushed the ball wide of the left-hand post, and the Reds survived. There were more difficult moments to come for the Jersey side, cheered on by a large contingent of visiting supporters, as Leeroy Atalifo earned a birthday present from the referee, who ruled the Fijian's first tackle after coming on as a replacement to be high and showed him a yellow card.
Showing good game management, the Reds were able to run down the sin-bin clock in relative comfort, although not without the need for more rock-solid defence. Restored to 14, and with the majority of the bench pressed into service, the Jersey maul again rumbled forward towards the Pirates' 22, and when the maul was illegally halted, Penberthy stepped forward to grab the ball and launch his decisive kick.
There was still time for Pirates to grab a late win, as they had in the recent Championship Cup tie at Stade Santander International, but the Cornishmen found the Reds' defence was resolute to the end, even during a period with 14 men after Kyle Hatherell went off with a head injury. Eventually the ball went into touch allowing Janco Venter to return as a HIA replacement, and the hosts launched a last desperate attack as the clock moved into added time; the slippery Javier Rojas Alvarez almost broke through, but a final handling error soon afterwards meant possession was lost, and the visitors only had to negotiate one last scrum and kick the ball off to secure the points.
The Reds strengthened their hold on third place after a round of games that otherwise saw home wins for lower-ranked sides, notably Yorkshire Carnegie over London Irish and Richmond over Ealing. Trailfinders' lead over Jersey is now 10 points, and the Reds are four points ahead of fourth-placed Bedford, with the Pirates another three points behind in fifth.
Cornish Pirates (1-15)
Marlen Walker, Dan Frost, Tyler Gendall, Toby Freeman, Brett Beukeboom (capt), Josh Caulfield, Matt Bolwell, Tom Duncan; Alex Day, Will Cargill; Matt Evans, Javier Rojas Alvarez, Rory Parata, Dan Koster; Maliq Holden.
Replacements: Alex Schwarz (for Day, 67 mins), Harvey Skinner (Cargill 67), John Stevens (Duncan 70), Sam Matavesi (Frost 70), Alex Cant (Evans 79). Not used: Jack Andrew, Danny Cutmore,
Jersey Reds (1-15)
Roy Godfrey, Charlie Maddison, Sam Rodman, Jerry Sexton (capt), Charlie Beckett, Kyle Hatherell, Rory Bartle, Janco Venter; Will Homer, Brett Herron; James Newey, Mark Best, Apakuki Ma'afu, Koch Marx; Leroy Van Dam.
Replacements: Leeroy Atalifo (for Rodman 47 mins, YC 51), Rodman (Newey 53-60 - sin-bin) Jack Macfarlane (Maddison 63), Liam Howley (Homer 63), Harry Morley (Godfrey 63), Aaron Penberthy (Herron 67), Conor Joyce (Venter 67), Dave McKern (Beckett 72), Venter (Hatherell 76, HIA)
REFEREE: Dean Richards. Assistants: Peter Brunt, Bill Burton
Half Time: 7-5
Try: Duncan 25
Conversion: Cargill 25
Try: Homer 20
Penalty: Penberthy 70
Why not get yourself a Hot Pot (Curry or Chilli served with rice) in the supporters marquee £8 per pot.