Grove had tasted Meon Valley Sunday League and League Cup defeats in two meetings with Waterlooville this term, but delivered when it really mattered to run out 4-3 final victors at Westleigh Park to claim the delayed 2019-20 season PDFA Vets Cup.
Paulsgrove looked to have it all wrapped up by half-time against the holders, racing into a 4-1 lead thanks to goals from Paul Smith, Steve Ledger, Brett Farley and Jon Taylor.
However, two second half penalties from Aaron Wright - following on from Mark Johnson's superb chipped leveller earlier in the contest - left Grove hanging on in the closing stages.
Smith made the most of a mistake by defender Nathan Willcox to power Paulsgrove ahead with a thunderous strike from just outside the area inside 10 minutes.
Waterlooville were level just six minutes later, though, with a goal of high quality. Goalkeeper Jamie Farrell spilt the ball before it found Johnson who exquisitely chipped into an empty net from around 30 yards out.
Ledger, who mixes veterans playing responsibilities with his role as Paulsgrove first team assistant manager, latched onto a defence-splitting Lee Cooper pass to slot past the onrushing Aaron Rogers and fire his team back ahead after 22 minutes.
Captain Farley headed home Paul Barton's pinpoint corner and Taylor fired into an empty net after a mistake by Rogers to put Paulsgrove in complete control as they led 4-1 at half time.
Social had much the better of the second half, seeing two goals disallowed for offside, before they reduced the deficit to 4-2. Tommy Aird went through the back of Johnson in the area, with Wright on hand to fire the resulting spot-kick past Farrell.
Wright slotted home another penalty with 10 minutes left and Waterlooville were then applying the pressure in search of an equaliser.
The holders were unable to find one, though, as Paulsgrove held on to edge a seven-goal thriller.
Paulsgrove: Farrell; Bishard, Bessy, Barton, Aird, P.Smith snr, Farley, P.Smith jnr, Taylor, Ledger, Cooper. Subs: Cole, Gofton, Samways, Ellis.
Waterlooville Social: Rogers; Berry, Willcox, Thumwood, Whitehouse, Smith, Johnson, Herd, Newton, Warwood, Wright. Subs: Braithwaite, Toghill, Budgen, King, Longhurst.