Cardiff made it a quickfire double over their near neighbours as they rattled up five tries without reply in the first-half to continue their good end to the season.
Having beaten Caerphilly 38-8 at the Arms Park eight days earlier, they matched that tally in the opening 40 minutes to pile on the points and consolidate their fourth place in the Welsh Premiership.
It was Wales full back Rhys Williams who started the early flourish as he ran in a solo try after 18 minutes. By the interval Dean Dewdney, Adam Jones, Don van Vuuren and Ryan Powell had followed suit.
It was not the kind of start that former Cardiff and Wales great Mark
Ring had been hoping for from his home side, especially as they have a major European final to come in two weeks time when they face Castres in the Parker Pen Shield final in Reading.
Things went from bad to worse shortly after the break when Wales utility back Iestyn Harris hoisted his match tally to 20 points with a try and a sixth conversion to further stretch the lead.
But far from throw in the towel, Caerphilly rallied and two more penalties from outside half Luke Richards gave them new hope. Then two tries in the space of four minutes, both converted by Richards, breathed new life into the final quarter.
Wing Ryan Howells crossed for the first of the home tries and then lock Darren Davies romped over moments after his opposite number Heino Senekal was sent to the sin-bin. But all that was left in the game were two more penalties from the two outside halves and Cardiff hung on for victory.
Caerphilly: Tries: R Howells, D Davies; Cons: L Richards 2; Pens: L Richards 6.
Cardiff: Tries: R Williams, D Dewdney, A Jones, D
van Vuuren, R Powell, I Harris; Cons: I Harris 6; Pens: I Harris 2.
As the countdown continues for RWC2015, Tournament Chief Executive Debbie Jevans visited the Millennium Stadium to discuss preparations for the eight matches and reveal the positive news that 100,000 tickets for games at the home of Welsh rugby have sold in the last seven days.
Jason Harries is targeting a first win on the World Series circuit this season with Wales. The series returns to action this weekend in Dubai where Harries is part of a team hoping to build from its efforts in round one in October.
Wales skipper Jevon Groves says his side have addressed a few points from Gold Coast and aim to 'hit the ground running' in the next two rounds of the World Series, kicking off with this weekend in Dubai before heading off to South Africa next week.
Wales Sevens manager Steff Thomas is hopeful his side can build from a quarter-final spot in the opening round of the World Series in Australia when his side take part in the forthcoming double header in Dubai and South Africa.